Have you checked the UCP to see if there is a newer revision? might not help but maybe. It will tell you the lastest revision and what issues were corrected. Bad thing is you can't flash it, you have to get the whole board. The last one I bought was over 400 bucks.
I have a lot of information on these micro controls. If you would like to check it out let me know.
I forgot to mention. One time with this same problem it was because the Trane digital thermostat was in the auto shift over mode. So I just set it to cool or heat mode and no more problems. If its far enough into the season the auto mode didn't really matter.
Then one time it was a bad compressor contactor. They were burnt just enough to cause it to be intermittent failure. Replaced them and it solved the problem.