Changing hides can be stressful, but it sounds like you need to do so.

These issues that you are having can be easily resolved by using identical hides throughout the cage. If they are all the same your snake can't favor one over the other. That way he will go to the hide that is the temperature that he wants.

I really like these hides, as they provide a lot of security for the snake, are easy to clean, and are cheap!

http://www.reptilebasics.com/hide-boxes

Just to make sure. Your UTH is being regulated by a thermostat correct? sometimes a snake will avoid the hot side because of an unregulated UTH that is way too hot.