Issue with Carrier infinity heat pump

zepfan

we are having an issue with a carrier infinity heat pump model# 38ydb060320.
installed in 2006. The issue the system runs fine for a few days, then locks out on Code 6 “thermal cut out in high stage. The unit is reset, and the unit restarts. I was out last week and the compressor was not hot at all. The system was running a 125-325 (410 a) with a 90 degree outside ambient. 10 degrees of subcooling, and 12 degree super heat. Everything seemed normal. According to the manual for the unit this could either be the overload in the compressor tripping prematurely, or the start relay not opening. I had a meter across the start capacitor and the relay seemed to open every time I cycled the unit. The unit ran fine for three days and then tripped out again today.
I guess the board could be bad, but was wondering if anyone else has had this issue? And is it possible to run the unit on just low stage? It never displays a cutout in low stage, and the home has several other systems, and this one appears to be oversized. This would just be a temporary fix as the homeowner knows based on the age of the heat pump, it will need to be replaced eventually.

The system has a communicating air handler attached to it (FE4A) and the first generation infinity user interface. Any suggestions would be much appreciated

Thanks to all