I may be totally wrong here but recently I set up a qt tub and put the tub on top of a metal grating of sorts - I quickly learned that the metal was interacting with the heat tape - every time I touched anything it would malfunction my Helix - I believe it was some sort of current between the heat tape and the conductivity of the metal - try using something less conductive like wood. I ended up putting my tub on a glass - it worked fine after that.

Just my thoughts.