MP3Tag Unable To Edit Tags On File?

[BlackFirePhenex]

I have been summoned!
TLDR: The creator changed the program to adhere to the mkv specifications. VLC and probably some other programs aren't doing that. To fix this compatibility issue a beta or alpha version of MP3Tag was created and linked.

Here is the link to the Post of the Developer:

MKV-"Title"Tag Bug in 3.29

Many thanks for your feedback! I've just released Mp3tag v3.29a which introduces an option for video-specific mappings for Matroska video via Options → Tags → Advanced. This is to increase compatibility with apps that, e.g., only read TITLE with target type T=30. @BlackFirePhenex, if you disable this option, Mp3tag should write TITLE as in v3.28 so that VLC and any other app that requires the track-level target-types can read and display the title.