They are always going to stand by their products at Spyder Robotics. They will test the unit and determine where the issues lie. 6 yrs is not a lot for the herpstat although I don’t know for sure what time frame the individual units are warrantied for. Mine have been working fine for the past 12 years. I have had to email them a couple of times and it turned out to be the old heat tape and not the thermostat. Has the unit been dropped or banged around that you know of? I’m sure they will give you the benefit of any doubt.