UTH won't stick

[Eric Alan]

My probe is on top of the glass below the substrate inside the aquarium. It is set for 93. I am seeing 92-93 on the parts of the uth that are properly attached to the glass but you can see where its not stuck well, and those parts around the edges are around 85....

Also the top of the substrate is only about 88 and I have barely any on it, but I don't want to turn up the UTH in case she burrows down to the glass.

The thermostat probe should be sandwiched between the bottom of the glass and the UTH (on the outside of the enclosure). You will have significantly more stable temperatures this way. Also, a range of 85-93 is perfectly fine. You just need to make sure it doesn't stray from there by moving the probe to where it needs to be. See the amazing drawing below for reference: