Once in a while the Metronome dropdown form will be stuck open and the screen will appear frozen, but it’s not. Just the Metronome dropdown form is stuck open and nothing else on the screen will respond to any touch (taps, pencil, or mouse).
The way I’ve found to clear this stuck screen object is to:
Press cmd+. (period).
cmd plus the period key sends the Esc key code to iPadOS.
Apple Smart Keyboard for my iPad doesn’t have an Esc key, so I found this equivalent looking through Mac keyboard shortcuts. In fact, there are a number of keyboard shortcuts for Mac which work on iPad OS, even though they’re not documented anywhere in iPad docs. This is true in Apple Numbers, Pages KeyNote and probably other Apple apps made for both Mac and iPad.
When needed, this is very helpful.
This is untested in Cubasis 3 running under Android.