White line on 4:3 videos

I have LibreELEC-RPi4.arm-9.1.002 running on a Pi 4 (4 GB) and it is generally working OK, but there is a major problem with most (not all) 4:3 videos that I play. It puts a white line on the right side of the video (between the video and the right-hand black bar).

This does not happen with my Android TV box running SPMC v16.7.4 or Kodi v18.3 (I've still got the Android TV set up so I can directly compare). The white line is not on the source videos because it is not present when played on my laptop via MPV or VLC. This suggests something is happening with LibreELEC or the Pi.

I've tried changing various settings including disabling hardware acceleration with nothing making a difference. Does anyone have any ideas or perhaps this is something that might be addressed in future builds?

I can upload logs if it would help anyone.

Here is a log for the problem:

Log

I play a few seconds of two videos during the course of this log, both consecutive episodes from the same series:

S7E19 - Q2.mkv - this does NOT have a white line

S7E20 - Author, Author.mkv - this DOES have a white line

Thanks for the suggestion in looking at the metadata, Da Flex. I did this and by looking at many videos I've now realised that the white line only appears on those 4:3 videos that are 10-bit HEVC. If they are AVC or even 8-bit HEVC then the white line does not appear.

It turned out that series I used as an example above oddly has a mixture of 8/10 bit videos.The video resolutions are not a factor because, for example, I compared two 704x572 HEVC videos, one 8-bit and one 10-bit, and only the 10-bit has the problem.

So something isn't handling 4:3 10-bit HEVC video correctly. Perhaps it is drawing white pixels instead of filling with black as you suggest, which it obviously shouldn't be doing. Seems unlikely to be Kodi as it's the same Kodi version on my Android TV box, so what could it be...LibreELEC or the Pi 4?

Thanks, I think I'll post a bug report.