@Twelfth Monkey: sorry, I completely missed your post until just now.
Good point! Though I haven't noticed any stuck buttons yet, residue on the screen could very well be a factor (though I'm wiping off the unit regularly with isopropyl alcohol).
I'll watch out for that!

Meanwhile I made a page containing PS debug panel and configured the wheel to print a message when it's triggered.
The idea was to switch to this page when I notice the issue and to see if there are any events issued by the wheel when the screen activates.
Unfortunately that doesn't seem to be the case. Either it's not the wheel or it wakes up the device without triggering a "scriptable event" (rotating the wheel manually gives me the expected output, so that works).

Sebastian

BTW, @Lyndel: did you get my email?