Post-Annotator: After sync, shorter video shows up as annotation in longer video
Screenshot below probably shows what the problem is. The video in the annotation item in the annotation stream is the video that is synced to the video opened in the Post-Annotator on the Timeline.
If you want to reproduce it, here are the video files used (there are two claps in the beginning that you can use for the sync):
https://assets.motionbank.org/vortanz/misc/Test-Ronja-schneidercorner.mp4