diff --git a/src/Model/Contact.php b/src/Model/Contact.php
index f96c556d24..ae715840eb 100644
--- a/src/Model/Contact.php
+++ b/src/Model/Contact.php
@@ -1166,6 +1166,12 @@ class Contact
 
 		self::updateFromProbeArray($contact_id, $data);
 
+		// Don't return a number for a deleted account
+		if (!empty($data['account-type']) && $data['account-type'] == User::ACCOUNT_TYPE_DELETED) {
+			Logger::info('Contact is a tombstone', ['url' => $url, 'uid' => $uid]);
+			return 0;
+		}
+
 		return $contact_id;
 	}
 
@@ -1770,20 +1776,26 @@ class Contact
 	 *
 	 * @param integer $id      contact id
 	 * @param integer $uid     user id
-	 * @param string  $url     The profile URL of the contact
+	 * @param string  $old_url The previous profile URL of the contact
+	 * @param string  $new_url The profile URL of the contact
 	 * @param array   $fields  The fields that are updated
 	 *
 	 * @throws \Exception
 	 */
-	private static function updateContact($id, $uid, $url, array $fields)
+	private static function updateContact(int $id, int $uid, string $old_url, string $new_url, array $fields)
 	{
+		if (Strings::normaliseLink($new_url) != Strings::normaliseLink($old_url)) {
+			Logger::notice('New URL differs from old URL', ['old' => $old_url, 'new' => $new_url]);
+			// @todo It is to decide what to do when the URL is changed
+		}
+
 		if (!DBA::update('contact', $fields, ['id' => $id])) {
 			Logger::info('Couldn\'t update contact.', ['id' => $id, 'fields' => $fields]);
 			return;
 		}
 
 		// Search for duplicated contacts and get rid of them
-		if (self::removeDuplicates(Strings::normaliseLink($url), $uid)) {
+		if (self::removeDuplicates(Strings::normaliseLink($new_url), $uid)) {
 			return;
 		}
 
@@ -1807,7 +1819,7 @@ class Contact
 		}
 
 		// Update contact data for all users
-		$condition = ['self' => false, 'nurl' => Strings::normaliseLink($url)];
+		$condition = ['self' => false, 'nurl' => Strings::normaliseLink($old_url)];
 
 		$condition['network'] = [Protocol::DFRN, Protocol::DIASPORA, Protocol::ACTIVITYPUB];
 		DBA::update('contact', $fields, $condition);
@@ -1870,7 +1882,7 @@ class Contact
 			Worker::add(PRIORITY_HIGH, 'MergeContact', $first, $duplicate['id'], $uid);
 		}
 		DBA::close($duplicates);
-		Logger::info('Duplicates handled', ['uid' => $uid, 'nurl' => $nurl]);
+		Logger::info('Duplicates handled', ['uid' => $uid, 'nurl' => $nurl, 'callstack' => System::callstack(20)]);
 		return true;
 	}
 
@@ -1941,14 +1953,14 @@ class Contact
 		// We check after the probing to be able to correct falsely detected contact types.
 		if (($contact['contact-type'] == self::TYPE_RELAY) &&
 			(!Strings::compareLink($ret['url'], $contact['url']) || in_array($ret['network'], [Protocol::FEED, Protocol::PHANTOM]))) {
-			self::updateContact($id, $uid, $contact['url'], ['failed' => false, 'last-update' => $updated, 'success_update' => $updated]);
+			self::updateContact($id, $uid, $contact['url'], $contact['url'], ['failed' => false, 'last-update' => $updated, 'success_update' => $updated]);
 			Logger::info('Not updating relais', ['id' => $id, 'url' => $contact['url']]);
 			return true;
 		}
 
 		// If Probe::uri fails the network code will be different ("feed" or "unkn")
 		if (in_array($ret['network'], [Protocol::FEED, Protocol::PHANTOM]) && ($ret['network'] != $contact['network'])) {
-			self::updateContact($id, $uid, $ret['url'], ['failed' => true, 'last-update' => $updated, 'failure_update' => $updated]);
+			self::updateContact($id, $uid, $contact['url'], $ret['url'], ['failed' => true, 'last-update' => $updated, 'failure_update' => $updated]);
 			return false;
 		}
 
@@ -1998,7 +2010,7 @@ class Contact
 		}
 
 		if (!$update) {
-			self::updateContact($id, $uid, $ret['url'], ['failed' => false, 'last-update' => $updated, 'success_update' => $updated]);
+			self::updateContact($id, $uid, $contact['url'], $ret['url'], ['failed' => false, 'last-update' => $updated, 'success_update' => $updated]);
 
 			if (Contact\Relation::isDiscoverable($ret['url'])) {
 				Worker::add(PRIORITY_LOW, 'ContactDiscovery', $ret['url']);
@@ -2039,7 +2051,7 @@ class Contact
 
 		unset($ret['photo']);
 
-		self::updateContact($id, $uid, $ret['url'], $ret);
+		self::updateContact($id, $uid, $contact['url'], $ret['url'], $ret);
 
 		if (Contact\Relation::isDiscoverable($ret['url'])) {
 			Worker::add(PRIORITY_LOW, 'ContactDiscovery', $ret['url']);
diff --git a/src/Model/Tag.php b/src/Model/Tag.php
index 8f132e82f3..451ed687b3 100644
--- a/src/Model/Tag.php
+++ b/src/Model/Tag.php
@@ -125,7 +125,9 @@ class Tag
 				// The contact wasn't found in the system (most likely some dead account)
 				// We ensure that we only store a single entry by overwriting the previous name
 				Logger::info('Contact not found, updating tag', ['url' => $url, 'name' => $name]);
-				DBA::update('tag', ['name' => substr($name, 0, 96)], ['url' => $url]);
+				if (!DBA::exists('tag', ['name' => substr($name, 0, 96), 'url' => $url])) {
+					DBA::update('tag', ['name' => substr($name, 0, 96)], ['url' => $url]);
+				}
 			}
 		}
 
diff --git a/src/Worker/ExpirePosts.php b/src/Worker/ExpirePosts.php
index 8d50c5d9d5..14fb560b13 100644
--- a/src/Worker/ExpirePosts.php
+++ b/src/Worker/ExpirePosts.php
@@ -22,7 +22,6 @@
 namespace Friendica\Worker;
 
 use Friendica\Core\Logger;
-use Friendica\Core\Worker;
 use Friendica\Database\DBA;
 use Friendica\DI;
 use Friendica\Model\Item;
@@ -46,54 +45,54 @@ class ExpirePosts
 		}
 
 		if (!empty($expire_days)) {
-			do {
-				Logger::notice('Start deleting expired threads', ['expiry_days' => $expire_days]);
-				$ret = DBA::e("DELETE FROM `item-uri` WHERE `id` IN
-					(SELECT `uri-id` FROM `post-thread` WHERE `received` < UTC_TIMESTAMP() - INTERVAL ? DAY
-						AND NOT `uri-id` IN (SELECT `uri-id` FROM `post-thread-user`
-							WHERE (`mention` OR `starred` OR `wall` OR `pinned`) AND `uri-id` = `post-thread`.`uri-id`)
-						AND NOT `uri-id` IN (SELECT `uri-id` FROM `post-category`
-							WHERE `uri-id` = `post-thread`.`uri-id`)
-						AND NOT `uri-id` IN (SELECT `uri-id` FROM `post-media`
-							WHERE `uri-id` = `post-thread`.`uri-id`)
-						AND NOT `uri-id` IN (SELECT `parent-uri-id` FROM `post-user` INNER JOIN `contact` ON `contact`.`id` = `contact-id` AND `notify_new_posts`
-							WHERE `parent-uri-id` = `post-thread`.`uri-id`)
-						AND NOT `uri-id` IN (SELECT `parent-uri-id` FROM `post-user`
-							WHERE (`origin` OR `event-id` != 0 OR `post-type` = ?) AND `parent-uri-id` = `post-thread`.`uri-id`)
-						AND NOT `uri-id` IN (SELECT `uri-id` FROM `post-content`
-							WHERE `resource-id` != 0 AND `uri-id` = `post-thread`.`uri-id`))
-					ORDER BY `id` LIMIT ?", $expire_days, Item::PT_PERSONAL_NOTE, $limit);
+			Logger::notice('Start collecting expired threads', ['expiry_days' => $expire_days]);
+			$uris = DBA::select('item-uri', ['id'], ["`id` IN
+				(SELECT `uri-id` FROM `post-thread` WHERE `received` < UTC_TIMESTAMP() - INTERVAL ? DAY
+					AND NOT `uri-id` IN (SELECT `uri-id` FROM `post-thread-user`
+						WHERE (`mention` OR `starred` OR `wall` OR `pinned`) AND `uri-id` = `post-thread`.`uri-id`)
+					AND NOT `uri-id` IN (SELECT `uri-id` FROM `post-category`
+						WHERE `uri-id` = `post-thread`.`uri-id`)
+					AND NOT `uri-id` IN (SELECT `uri-id` FROM `post-media`
+						WHERE `uri-id` = `post-thread`.`uri-id`)
+					AND NOT `uri-id` IN (SELECT `parent-uri-id` FROM `post-user` INNER JOIN `contact` ON `contact`.`id` = `contact-id` AND `notify_new_posts`
+						WHERE `parent-uri-id` = `post-thread`.`uri-id`)
+					AND NOT `uri-id` IN (SELECT `parent-uri-id` FROM `post-user`
+						WHERE (`origin` OR `event-id` != 0 OR `post-type` = ?) AND `parent-uri-id` = `post-thread`.`uri-id`)
+					AND NOT `uri-id` IN (SELECT `uri-id` FROM `post-content`
+						WHERE `resource-id` != 0 AND `uri-id` = `post-thread`.`uri-id`))",
+				$expire_days, Item::PT_PERSONAL_NOTE]);
 
-				$rows = DBA::affectedRows();
-				Logger::notice('Deleted expired threads', ['result' => $ret, 'rows' => $rows]);
+			Logger::notice('Start deleting expired threads');
+			$affected_count = 0;
+			while ($rows = DBA::toArray($uris, false, 100)) {
+				$ids = array_column($rows, 'id');
+				DBA::delete('item-uri', ['id' => $ids]);
+				$affected_count += DBA::affectedRows();
+			}
+			DBA::close($uris);
 
-				if (!Worker::isInMaintenanceWindow()) {
-					Logger::notice('We are outside of the maintenance window, quitting');
-					return;
-				}
-			} while ($rows >= $limit);
+			Logger::notice('Deleted expired threads', ['rows' => $affected_count]);
 		}
 
 		if (!empty($expire_days_unclaimed)) {
-			do {
-				Logger::notice('Start deleting unclaimed public items', ['expiry_days' => $expire_days_unclaimed]);
-				$ret = DBA::e("DELETE FROM `item-uri` WHERE `id` IN
-					(SELECT `uri-id` FROM `post-user` WHERE `gravity` = ? AND `uid` = ? AND `received` < UTC_TIMESTAMP() - INTERVAL ? DAY
-						AND NOT `uri-id` IN (SELECT `parent-uri-id` FROM `post-user` AS `i` WHERE `i`.`uid` != ?
-							AND `i`.`parent-uri-id` = `post-user`.`uri-id`)
-						AND NOT `uri-id` IN (SELECT `parent-uri-id` FROM `post-user` AS `i` WHERE `i`.`uid` = ?
-							AND `i`.`parent-uri-id` = `post-user`.`uri-id` AND `i`.`received` > UTC_TIMESTAMP() - INTERVAL ? DAY))
-					ORDER BY `id` LIMIT ?",
-					GRAVITY_PARENT, 0, $expire_days_unclaimed, 0, 0, $expire_days_unclaimed, $limit);
+			Logger::notice('Start collecting unclaimed public items', ['expiry_days' => $expire_days_unclaimed]);
+			$uris = DBA::select('item-uri', ['id'], ["`id` IN
+				(SELECT `uri-id` FROM `post-user` WHERE `gravity` = ? AND `uid` = ? AND `received` < UTC_TIMESTAMP() - INTERVAL ? DAY
+					AND NOT `uri-id` IN (SELECT `parent-uri-id` FROM `post-user` AS `i` WHERE `i`.`uid` != ?
+						AND `i`.`parent-uri-id` = `post-user`.`uri-id`)
+					AND NOT `uri-id` IN (SELECT `parent-uri-id` FROM `post-user` AS `i` WHERE `i`.`uid` = ?
+						AND `i`.`parent-uri-id` = `post-user`.`uri-id` AND `i`.`received` > UTC_TIMESTAMP() - INTERVAL ? DAY))",
+				GRAVITY_PARENT, 0, $expire_days_unclaimed, 0, 0, $expire_days_unclaimed]);
 
-				$rows = DBA::affectedRows();
-				Logger::notice('Deleted unclaimed public items', ['result' => $ret, 'rows' => $rows]);
-
-				if (!Worker::isInMaintenanceWindow()) {
-					Logger::notice('We are outside of the maintenance window, quitting');
-					return;
-				}
-			} while ($rows >= $limit);
+			Logger::notice('Start deleting unclaimed public items');
+			$affected_count = 0;
+			while ($rows = DBA::toArray($uris, false, 100)) {
+				$ids = array_column($rows, 'id');
+				DBA::delete('item-uri', ['id' => $ids]);
+				$affected_count += DBA::affectedRows();
+			}
+			DBA::close($uris);
+			Logger::notice('Deleted unclaimed public items', ['rows' => $affected_count]);
 		}
 	}
 }
diff --git a/src/Worker/MergeContact.php b/src/Worker/MergeContact.php
index ee66abed37..6c30b9b917 100644
--- a/src/Worker/MergeContact.php
+++ b/src/Worker/MergeContact.php
@@ -71,7 +71,6 @@ class MergeContact
 			if (DBStructure::existsTable('thread')) {
 				DBA::update('thread', ['author-id' => $new_cid], ['author-id' => $old_cid]);
 				DBA::update('thread', ['owner-id' => $new_cid], ['owner-id' => $old_cid]);
-				DBA::update('thread', ['causer-id' => $new_cid], ['causer-id' => $old_cid]);
 			}
 		} else {
 			/// @todo Check if some other data needs to be adjusted as well, possibly the "rel" status?