It seems that after a couple hours of use it starts to freeze notes and eventually the entire synth stops responding.
Have you checked for midi loops?
Whats that?
I don’t know how Live works, but in Cubase when you have a midi connection you can filter out some midi messages from incoming and outgoing. To prevent incoming midi from being replicated out, so that the midi sent is not returned back again in a loop.
Loops can cause strange behaviour. I can imagine stacked midi data causing errors after a while …