Regression: mute and solo don't work in the mixer

In my 3.0 (self compiled), If I bring up the mixer and press Mute or Solo on any of the instruments, and then press play, I don't observe any effect. The instruments do not seem to be muted at all.
Also there does not seem to be any indication on the form itself that I've pressed Mute. I.e., it does not appear to be a boolean toggle button.

I'm attaching the score I used to observe this problem.

The same issue is discussed here: https://musescore.org/en/node/127091#comment-577586