When PFL is clicked on a Player, the PFL dialog opens.
While the PFL dialog is open, you can click the PFL button on a different Player and usually, this does not cause any problems and simply changes PFL to the newly selected Player.
HOWEVER…
If the PFL Player is changed rapidly by clicking PFL buttons on Players rapidly, it seems the PFL dialog can become ‘confused’ and be PFLing >1 Player at the same time. When the PFL button is clicked again to close the PFL dialog, all mAirList (and probably BASS) audio is ‘choppy’ and this cannot be fixed except by reboot (logoff and log on does NOT cure it).
Can I suggest that:
a) the PFL dialog is changed to application modal, and
b) the PFL dialog is given an X Close button?
The user cannot then change the selected Player while the PFL dialog is open, preventing the possibility of the problem described above.
There is no reason to prevent two players being in PFL at the same time. People might want to pre-listen segues etc. Clicking PFL while another PFL is active does not close the first PFL, the players are just PFLing at the same time (and the second PFL window will overlap the first, but you can move it with the mouse).
However, the players should not interfere with each other or cause any crashes. I will investigate that.
I think you may have identified the problem! Because they overlay exactly, I had (wrongly) thought that there was only ever one PFL window, whose Title Bar changed. The possibility of >1 PFL dialog in a neat z-stack had not occurred to me!
I would still prefer the PFL window to have an X Close button on it. It is not obvious—especially to new users—that you need to click the Player PFL button a second time to close the PFL window.