Comment does not get saved when PDF is open

I’m having an issue since I’ve updated to NextCloud 20. When I create a comment when a PDF is open the comment does not get saved. But the problem only occurs when the side window was already open before opening the PDF.

I’ve created a short video that shows the problem and uploaded it to YouTube: NextCloud Comment not saved - YouTube

Is anyone else experiencing this problem or has this something to do with my Nextcloud configuration?

Does no one else have this problem?