Plex makes beta releases available to users with a Plex Pass.
I don’t run Plex in Docker, but from what I understand, if the container supports and is configured to use the beta release, then that is the one you’ll get.
Beta releases are, by their nature, less tested than public releases. It is expected that problems will crop up.
As mentioned in the release notes, PMS 1.43 is a rather large update. Plex updated the transcoder from FFMPEG 4.x to FFMPEG 6.1. The 1.43 release will stay in beta for an extended period to better shake out any problems with the new transcoder.
