Under certain circumstances, stale sync events can occur, and those events will then accumulate in the event queue list (see attached screenshot). These can occur in many
different circumstances. Here is one case where this was detected, using eZ Publish 4.7 / eZ Content Staging 4.7.1:
1. Source & target: installed fix from issue
2. Source & target: modified content.ini.append.php:
3. Source: created a new article, with 4 versions;
4. Source: Synced the resulting 4 events. Got he following output:
Events 3 and 4 are correctly processed, but events 1 and 2 are invalid and will remain on the queue.