I may have missed something the t-stat probe is in on the glass above the UTH? It should be on the glass or outside. Typical of everything there are 2 schools of thought. One is to place the T-stat probe inside and one outside. If you place it inside it should be at the very bottom and be absolutely secure. I use hot melt glue to to that job. The thermometer probe I place inside the hot hide on the substrate. I don't keep tons of substrate over the uth so heat transfers efficiently.