Maybe this will help. Balls spend most of their time in their hides. Usually only leaving to find food and water and an occasional exploration/escape attempt. IMO it's nothing to worry about hes probably out and about the cage around 4 am and you just haven't seen him. Or you may have a snake that knows it's winter time and is "hybernating". If he's still eating and is hydrated you probably don't have anything to worry about, he's doing what balls do.
With that being said: Screen tops don't work for balls, it lets out too much heat and humididty, put a towel or board or something over it. Second I see an analog thermometer in the cage, had one just like it once, it sucks and is not accurate, get a good digital dual prong thermometer/hygrometer. You're humidity needs to be uped to about 60% and that light will suck a lot of humidity out of the air. The basking light may also be too hot for your snake, do you have any belly heat going? Maybe you can try turning the light off for some time see if that will get him to come out.
This is just my opinion, Hope this helps.
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Tosha 
1.1.0 Ball Python (Harry and Fluffy)
0.1.0 Siberian Husky (Kita)
0.2.0 Feline (Pippen and Pandora)
0.0.1 Dessert Tortoise (Pope)
5.4.2 Fish (1,2,3,4...)
0.0.1 Frog rescued from pool skimmer
0.0.2 Lizards rescued from pool skimmer