Pre Heat issues with V605?

The problem was the PH not getting to set temp as the thermal sensor cuts out before reaching PH value. Replacement induction fan with larger capacity worked for four b2b roasts then problem reoccurred on 5th b2b PH. USB fan pointed at control panel underneath drum still solves the issue, so thermal sensor must still be playing havoc with something

I apologise if this is a stupid question, but does this happen with any firmware or, as the title suggests, just with 605? I understand that you already went through with the warranty fix, but Iā€™m just curious.