I've had this happen to me before (and reported it, just to be told, by PGMusic support, that it was by design)...

When I right click on the description of a track that I want to change, instead of right clicking on the track name... The focus of the track doesn't shift.

However, the right click menu does come up, on the track that you right clicked on, and it makes you think that you are changing instruments on that track. But you are really modifying the track previously highlighted (because to focus didn't change when you right clicked on the track that you thought you were modifying.

Apparently this is "By Design"... See attached screen shots...

Attached Files (Click to download or enlarge) (Only available when you are logged in)
Screenshot 2021-04-01 141835.jpg (205.56 KB, 118 downloads)
PGMusic Response.jpg (222.52 KB, 119 downloads)