Your ball python is seeking security. Because the hot side is a little too warm (maybe bump it down to 90 on the warm side) for him to be all the time, he's traveling to the cool side. Most ball pythons prefer the cool side unless they are digesting. You need to add another hide (preferably identical to the hot hide) on the cold side so your ball python can still sit on the cold side and yet still feel secure. As a note: you only need a humid hide when they are in shed.
Here's my advice to you to help your BP be as happy as a clam:
- get rid of the humid hide - he only needs it in shed and sitting on wet moss all the time can give him scale rot if you aren't careful
- get an identicle hide on the cold side of the tank - he needs to be able to thermoregulate and yet feed his need for security.
- try to bump the warm side down maybe a degree. Some don't like it too warm. I usually keep my hot spot around 90-91.
- You really don't need a heat mat on the cold side. What you need to do is heat the AMBIENT temperature over 75. You can do that by adding a heat lamp or a CHE on a dimmer. This will lower your humidity, so be watchful of that. This will help give an even gradient. Your heat mat only heats the surface of your substrate. So really, you're snake is going from a 91 hotspot to about 75 in the middle then about 80 on end. Your ambient temperature is still 75 because the heat mat is not heating the air.
I hope hope that made a little bit of sense.