For some reason, the TV Episode is always getting set to 1\06 where 1 is the season and 06 is the episode, although the TV Episode column only shows a 1 (the season) but the left side shows the 1\06
The double backslash \\ is a placeholder character showing that you have two fields named episode. Something in your actions is writing a second field.
Knowing it is somewhere in the action now, I would try to simplify things. Create a new action and add one line at a time and run it. When the unexpected results happen it will be from the last line added.
In your screenshot I see an empty line between TVEPISODE and TVSEASON - what could that be?
Also, I see no field TRACK although you set it with an action - could it be that the TVEPISODE is mapped to TRACK (or vice versa)?
Yes, Matroska video MKV has a mapping from TVEPISODE to Matroska's PART_NUMBER on the T=50 target type (used for episodes for TV series as outlined in the Matroska Tags technical documentation).
This mapping is also used when writing DISCNUMBER, which results in duplicate TVEPISODE values for MKV files.
Seeing this now makes more sense, given the recent changes in mp3tag for handling mkv files. There was no mmention of this earlier and I didn't think to ask. Glad this was worked out.
With the new mkv mappings, does this mean there is now no way to indicate disc numbers for multi-disc packages? TV show collections often have many seasons and often each season needs several discs.
I suppose this isn't so important in the grand scheme of things, as long as the season and episode numbers work to keep things in order. It just drops the original disc information.
Yes. If I'd remove the mapping of DISCNUMBER to Matroska's PART_NUMBER on the T=50 target type for MKV files, everything that now reads from and writes to DISCNUMBER would use a user-defined field.