Drum Visibility Agent bug in lower zone

The Drum Visibility Agent “Show Drum Sounds with Events” does not work in the lower zone, unless a separate drum
edit window is open.

to test, open drum editor in lower zone, and also open a new drum edit window (open in separate window), select Drum Visibility agent to “show drum sounds with events” (using GM drum map, with maybe just a kick and snare active) - so far all good,
but close the separate drum edit window, and then the lower zone drum visibility agent goes back to show all, even though it is set to only show with events,
Open the separate window again and the lower zone then shows OK again.