May be related, maybe not, but as I have an LX88, thought I'd share this story just in case...
I use my LX88 in a live setup with a laptop running SONAR. It had worked just fine for a few gigs and practice setups, spread out over a couple years. The SONAR integration had worked just fine too, from the start. Then one day a couple months ago after hooking it back up and playing a couple minutes, it would just hang up, with any held notes just droning on forever until I quit SONAR. It was a really hard problem to pin down, as SONAR didn't exactly crash, and it was happening on every synth plugin that was running, and after a seemingly random number of minutes of playing after a cold start.
After a good night's sleep it occurred to me to try to reproduce the problem while running MIDI-OX, to see if the MIDI stream would tell me anything. Sure enough, it hung again, and then the clue revealed itself: when it hung up, it would always happen on a Sustain Pedal Down event. What in the world? I then confirmed by playing with the original SONAR setup, and sure enough, I would get beautiful music and no hangs as long as I never pressed on that sustain pedal.
My mind started to race... I started to think that my LX88 somehow went bad somewhere in its sustain circuit. I started to file through my order history to see if it was still under warranty. Nope. Dang! Then as I thought about the LX88's sustain circuit, as is oft the case, my thoughts went backward up the chain, and then drifted out through the Sustain Pedal Jack, down the cord, and then stopped at the pedal. Could it be? It *was* after all a rather cheap-o pedal, one from Hosa that I had picked up expressly for live gigs:
Dripping with curiosity, I ran down to the basement studio and pulled a known-to-be-good M-Audio SP-2 sustain pedal from the controller on my desk. My heart racing from the thrill of the hunt, I ran back up, yanked that Hosa out of the jack, plugged the SP-2 in the LX88, and commenced playing and sustaining. Guess what? No hangs. Even after hours of practice (and then performance) with *lots* of sustains.
My best guess as to what happened is that the switch contacts in the Hosa got dirty or corroded, which made the switch chatter, enough so to overwhelm the switch debouncing algorithm in the LX88 controller's firmware. In retrospect, that is a remarkable thing, that a switch could be that bad, and/or that it could overrun a processor's debounce buffer to the point that it would CRASH the keyboard's own internal firmware OS. It speaks to me of firmware that did not go through as rigorous a testing cycle as perhaps it should have. They do say hindsight is 20-20, but quite frankly, in over 40 years of playing, I've never had a keyboard crashed by a sustain pedal. Until now.
To the OP - based upon your system's symptoms, your issue is probably a bit different, but based on this experience, you may try to see if a MIDI-OX trace would reveal something of value?