Some development going on:
The team is now working on a thumbnail solution when using RTSP for LiveTV. Updated version can be found in the 2nd post:
https://forum.team-mediaportal.com/threads/improved-mediaportal-thumbnailer.113717/#post-930752
This is working for me almost perfectly.
In video shares view when a thumbnail is created it is left in the video directory, the setting in MPConfig for not leaving a thumbnail is ignored. It doesn't leave a thumbnail in the TV recording folder though.
Every now and then a file will fail (only 2 or 3 in the last week), but after clearing the blacklist and trying again it works. How long is a file blacklisted for, does it try again in a few hours or never?