Was there any resolution to this?
I just ran tuning having swapped my V1 tool board for a V1.1 and fitting a new power supply and get the same thing the heater faults every time anywhere between 60 and 100 degrees. Replacing the new M307 parameters with the old works OK
With Q600 I get motion between 45 and 100, although the servo range of motion is only about 60 degrees. This is good enough for me. With this setup I make 45% my "open valve (low pressure)" and 100% my "closed valve (high pressure)"