[JamesPeters]

This might have been mentioned before, but I didn't see it being mentioned:

For a particular track, change the number of track channels from 2 to a higher number (something that would noticeably increase the width of the MCP for the track). The MCP is cropped awkwardly until closing/opening the mixer again (at which point the MCP is widened and uncropped). It's more noticeable with "meter expansion" enabled since the MCP becomes a lot wider with more channels added.

Also if a track's MCP is wider due to having more channels, then you reduce the number of channels noticeably, it leaves some "blank panel space" (looks like a thick border on one side) until you close/open the mixer.

Something similar happens when allowing an MCP layout to automatically become a sidebar when selected (or not). The MCP will widen ok to become a sidebar type, but upon reverting to "standard" non-sidebar, there's extra "blank space" until the mixer is closed/opened again.

I'm using version 1.11 of the alpha theme, and Reaper for Linux x86-64 (v5.980+dev0717a). If you can't reproduce I can record a video (I can reproduce this consistently.)

Also there's this little thing I just noticed (see attached). That square appears when "element labels" is unchecked, and adding more track channels than 2. It's larger when you have more track channels (for this example it was 16, I think).