We have, over the years, installed many different manufactures' ductless heat pump systems. As of recently, we are using LG's ductless heat pumps. We have had a number of sensor failures on these systems--in multiple applications and at different jobs. I am not sure why. Upon changing them out the problem seems to be resolved. Is anyone else having these issues?
While I haven't had any problems, you might want to check with the manufacturer as to failures of the sensors. If yours are failing, maybe others have the same problem. Would not be the first time problems are happening at the manufacturers end.