I have had this problem playing on the chromatic keyboard as well, seems to happen when two adjacent notes are played in sequence fairly quickly, one right after the other (kind of in a legato style). Sometimes it happens, sometimes not. Try doing quick little two-note combos, using notes that are physically right next to each other, and see if you can replicate. I was able to replicate numerous times last time I intentionally tried, like a week ago. Can’t tell if it’s based on some very specific timing scenario or the notes being close to each other, or if it’s just a totally random thing, but I was definitely able to make it happen multiple times.
I wonder if it’s something that’s happening to a lot of people and they don’t even realize it because they’re mostly going to be using finite samples that end anyway, even if the length is set to 128, whereas single-cycle waveforms will go on forever.
Might be worth trying to set your sample to just regular “forward play”, not loop, and change it to a sample, not a waveform, then live-record and try to capture a hung note, maybe see if it’s happening with all samples or just single-cycles, or just “forward loop” or something? Might be kind of tedious I guess, but in the name of science! Probably would want to set the default sample length real short, so if you do get a random “128 length” you’ll hear the difference and can go back and look at the recorded trigs to confirm?
Didn’t really think of all this at the time, but I’m gonna go back and try some of these scenarios. Will report my findings.