This is contrary to what most people say/believe but I had my ball python in a 40 gallon tank when he was 1 month old and he did perfectly fine in there. His humidity was at 55%, a hide on the warm side at 90 degree and a hide on the cool side at 80 degrees, hides were nice and small, perfect for his size. He had branches to climb and everything. He started off as a clumsy climber but got better when he got longer, his falls were never more than 1 foot so he never got hurt. The questions Stewart_Reptiles asked will help a lot in knowing what the issue may be. I do believe some ball pythons need to start in a smaller enclosure especially if they've lived in a tub-like enclosure for a while before adopting as they are used to a small space.