I have an arctic spa with an inaccurate temp level on the screen. When it is set at 104 it only gets to 90ish. I purchased a new regulation probe and have been sticking it in the top of the tub. Same issue. If I pull it outside the heater kicks on and I can get the tub very hot...111. Currently the tub is at 100deg set at 104 (not heating anymore) and the display reads 107 degrees. I am checking true temp with a quality meat thermometer. Any suggestions?