I just saw you said the UTH is inside the tank. THATS DEAD WRONG!!!! WHY DO YOU THINK THATS THE CORRECT WAY?
Being new to snakes you should spend some time and see that most long time keepers place the probes for uth's outside the cages. This is because they have learned through trial and error and outside is by far the safest way to set it up.
Like it was already said even Spyderobotics even tells you to place the probe outside the cage.
I have personally tried both ways and I had issues with the probes in the tank but not once have I had an issue with the probe on the outside.