Thanks for your response, Orca.
I've been noticing the missing audio in extras for some time now, but never realy followed up on it.
I am pretty sure that I changed severall versions of PMS since. The F series was on 2.0.5 since a couple of days, I updated it to 2.0.7 before i started the thread. The JS is on 2.0.7.
As it concerns the souce files: every extra I tried so far was affected (i tried a lot of different ones) and every one of them was transcoded. As the tv in the living room is occupied now, I can't test whether playback would be transcoded here as well.
I wish I would have stayed with the linuxserver/plex docker image, as it allows easy up and downgrade of the pms version.
Probably it's time to stop the watchtower container (auto updates images of running containers, deletes the old container and summons a new container with the settings of the old one) and downgrade to a previous image.