Bosch BCC100 doesn't stop heating call once target temp reached

JoshC

Hi folks. I had a Bosch IDS electric heat pump and air handler installed about 3.5 years ago for a pretty vanilla 1800sf house here in Central Virginia. Made the Nest mistake originally, but dumped that in mid-2020 for a Bosch BCC100. Had my local HVAC techs out to check the system out last summer, all fine.

It behaved okay for a while, but recently in heating mode it's been just flat ignoring when the target temperature is reached — I'll bump it up from say 70° to 72°, do some work, go out for a bit, then come back a few hours later and the thermostat reads 76°, still with 72° as the target, and the heat is still running flat-out. Sometimes first stage, sometimes even second stage. Only thing that stops it is cycling the system off and back on.

I guess what I'm asking is, is there any known DIY fix here — is there a software update out for the stat that's intended to fix this, anything like that — or is it time to call the tech and tell him to bring a Honeywell when he comes?