Tado keeps overheat

Hi.

I've got problem with my tado thermostat.

It looks like it stops responding and keep heating up and only way to stop it it to swich the power supply off to extension box and boiler.

It happens randomly.

I contacted tado support, but they useless. Keep saying that 3way Vale stuck. I knew that is not the case. But changed it anyway. Problem still remains.

Has anyone ever got the same issue?