diff --git a/src/Model/Post/User.php b/src/Model/Post/User.php
index 9da9718068..7bd5706997 100644
--- a/src/Model/Post/User.php
+++ b/src/Model/Post/User.php
@@ -24,7 +24,6 @@ namespace Friendica\Model\Post;
 use Friendica\Database\DBA;
 use \BadMethodCallException;
 use Friendica\Database\Database;
-use Friendica\Database\DBStructure;
 use Friendica\DI;
 
 class User
@@ -44,10 +43,6 @@ class User
 			throw new BadMethodCallException('Empty URI_id');
 		}
 
-		if (DBA::exists('post-user', ['uri-id' => $uri_id, 'uid' => $uid])) {
-			return false;
-		}
-
 		$fields = DI::dbaDefinition()->truncateFieldsForTable('post-user', $data);
 
 		// Additionally assign the key fields
@@ -59,6 +54,33 @@ class User
 			$fields['unseen'] = false;
 		}
 
+		// Does the entry already exist?
+		if (DBA::exists('post-user', ['uri-id' => $uri_id, 'uid' => $uid])) {
+			$postuser = DBA::selectFirst('post-user', [], ['uri-id' => $uri_id, 'uid' => $uid]);
+
+			// We quit here, when there are obvious differences
+			foreach (['created', 'owner-id', 'author-id', 'vid', 'network', 'private', 'wall', 'origin'] as $key) {
+				if ($fields[$key] != $postuser[$key]) {
+					return 0;
+				}
+			}
+			
+			$update = [];
+			foreach (['gravity', 'parent-uri-id', 'thr-parent-id'] as $key) {
+				if ($fields[$key] != $postuser[$key]) {
+					$update[$key] = $fields[$key];
+				}
+			}
+
+			// When the parents changed, we apply these changes to the existing entry
+			if (!empty($update)) {
+				DBA::update('post-user', $update, ['id' => $postuser['id']]);
+				return $postuser['id'];
+			} else {
+				return 0;
+			}
+		}
+
 		if (!DBA::insert('post-user', $fields, Database::INSERT_IGNORE)) {
 			return 0;
 		}
diff --git a/src/Protocol/ActivityPub/Processor.php b/src/Protocol/ActivityPub/Processor.php
index 9d5f3f2f6e..d1c3994e2a 100644
--- a/src/Protocol/ActivityPub/Processor.php
+++ b/src/Protocol/ActivityPub/Processor.php
@@ -45,7 +45,9 @@ use Friendica\Protocol\Activity;
 use Friendica\Protocol\ActivityPub;
 use Friendica\Protocol\Relay;
 use Friendica\Util\DateTimeFormat;
+use Friendica\Util\HTTPSignature;
 use Friendica\Util\JsonLD;
+use Friendica\Util\Network;
 use Friendica\Util\Strings;
 use Friendica\Worker\Delivery;
 
@@ -301,6 +303,11 @@ class Processor
 			Logger::notice('Parent not found. Try to refetch it.', ['parent' => $activity['reply-to-id'], 'recursion-depth' => $recursion_depth]);
 			if ($recursion_depth < 10) {
 				$result = self::fetchMissingActivity($activity['reply-to-id'], $activity, '', Receiver::COMPLETION_AUTO);
+				if (empty($result) && self::ActivityIsGone($activity['reply-to-id'])) {
+					// Recursively delete this and all depending entries
+					Queue::deleteById($activity['entry-id']);
+					return [];
+				}
 				$fetch_by_worker = empty($result);
 			} else {
 				Logger::notice('Recursion level is too high.', ['parent' => $activity['reply-to-id'], 'recursion-depth' => $recursion_depth]);
@@ -452,6 +459,24 @@ class Processor
 		return $item;
 	}
 
+	/**
+	 * Check if a given activity is no longer available
+	 *
+	 * @param string $url
+	 *
+	 * @return boolean
+	 */
+	private static function ActivityIsGone(string $url): bool
+	{
+		$curlResult = HTTPSignature::fetchRaw($url, 0);
+
+		if (Network::isUrlBlocked($url)) {
+			return true;
+		}
+
+		// @todo To ensure that the remote system is working correctly, we can check if the "Content-Type" contains JSON
+		return in_array($curlResult->getReturnCode(), [404]);
+	}
 	/**
 	 * Delete items
 	 *
@@ -933,6 +958,9 @@ class Processor
 				$success = true;
 			} else {
 				Logger::notice('Item insertion aborted', ['uri' => $item['uri'], 'uid' => $item['uid']]);
+				if (Item::isTooOld($item) || !Item::isValid($item)) {
+					Queue::remove($activity);
+				}
 			}
 
 			if ($item['uid'] == 0) {
diff --git a/src/Protocol/ActivityPub/Queue.php b/src/Protocol/ActivityPub/Queue.php
index 3d40d71638..7b91609bdb 100644
--- a/src/Protocol/ActivityPub/Queue.php
+++ b/src/Protocol/ActivityPub/Queue.php
@@ -116,7 +116,7 @@ class Queue
 	 * @param integer $id
 	 * @return void
 	 */
-	private static function deleteById(int $id)
+	public static function deleteById(int $id)
 	{
 		$entry = DBA::selectFirst('inbox-entry', ['id', 'object-id'], ['id' => $id]);
 		if (empty($entry)) {
@@ -206,7 +206,7 @@ class Queue
 		$entries = DBA::select('inbox-entry', ['id', 'type', 'object-type', 'object-id', 'in-reply-to-id'], ["`wid` IS NULL"], ['order' => ['id' => true]]);
 		while ($entry = DBA::fetch($entries)) {
 			// We don't need to process entries that depend on already existing entries.
-			if (!empty($entry['in-reply-to-id']) && DBA::exists('inbox-entry', ['object-id' => $entry['in-reply-to-id']])) {
+			if (!empty($entry['in-reply-to-id']) && DBA::exists('inbox-entry', ["`id` != ? AND `object-id` = ?", $entry['id'], $entry['in-reply-to-id']])) {
 				continue;
 			}
 			Logger::debug('Process leftover entry', $entry);
diff --git a/src/Worker/Cron.php b/src/Worker/Cron.php
index c2109e66a3..2ace97d830 100644
--- a/src/Worker/Cron.php
+++ b/src/Worker/Cron.php
@@ -92,6 +92,9 @@ class Cron
 			// Remove old pending posts from the queue
 			Queue::clear();
 
+			// Process all unprocessed entries
+			Queue::processAll();
+
 			// Search for new contacts in the directory
 			if (DI::config()->get('system', 'synchronize_directory')) {
 				Worker::add(PRIORITY_LOW, 'PullDirectory');
@@ -129,9 +132,6 @@ class Cron
 				Worker::add(PRIORITY_LOW, 'OptimizeTables');
 			}
 
-			// Process all unprocessed entries
-			Queue::processAll();
-
 			// Resubscribe to relay servers
 			Relay::reSubscribe();