Yes I use a glass tank, yes I know its not the greatest in the world to keep him in a glass tank.
He has an undertank heater and i use a tank thermometer, I have a heat lamp I was using before if that needs to be added but he also uses both sides, and i find him actually using his cool side hide more than his heated side. Is it possible the uth is getting too hot for him and he's retreating to the cool side even though its colder than it should be?