Ok, so from memory, the issue I stumbled upon was related to tracks in a folder. When trying to unsolo a track in a folder, first click resulted in a strange solo state that was totally unexpected. I had to then click again back to solo and then unsolo the second time and it was fine then. These might be two separate bugs, or can have the same root, idk.
Would have posted the reply sooner but apparently I had to wait again until Win10 finishes it's another cumulative updates crap. Hate when it's doing it even while Cakewalk open.