When both MIDI and Synth tracks are displayed in PRV, invoking Mute or Solo acts oddly or completely different that Track View behavior.
Actual: Activating a MIDI track M or S button does not activate the corresponding Synth's button until the mouse hovers over it. Then it's activated without actually clicking it.
Expected: Activating it should activate the other, as it does in Track View.
EDIT: This may only be a graphical issue.