It’s not that they cant climb or don’t… but they are not arboreal and too heavily bodied as adults. Juveniles have been seen climbing and eating birds in the wild but they are much small than their adult counterparts. I also always recommend checking husbandry when they do things that are not "normal"for their species. They may be trying to get closer to a heat source if they are constantly in the air for instance.
That was my first thought as well, I have quite a few around his age but he is the only one that does it. Temps, humidity are fine. Sides and back of tank is blacked out. He’s a strange little guy for sure.
I have an area in my yard designed for the snakes to be able to climb. Myself and my employees spend a lot of hours outside with the snakes. I have several videos of ball pythons climbing to impressive heights on IG. It’s specific to the anima and some never will. Heavy bodied adults almost always won’t. Smaller adult males that are inclined to climb will continue to do it throughout life. Based on what I’ve observed it is sometimes opportunity seeking and sometimes they seem to be fleeing predation.
If that spot it’s hanging from is under the lamp it’s climbing because it’s cold.
If you have CHE or overhead heat source then it could be climbing for heat. Otherwise it could just like climbing, each individual snake’s different. Do you have cover in the tank? If so and it doesn’t feel exposed in other places it’s likely the snake’s preference.
All of mine enjoy a climb, and friends who have them too. I never hear they don’t climb here in the uk haha, it’s always they like to climb! 
They’re tree pythons really you see…
Yea there is a lot of cover. 2 hides, a lot of plants as well
In that case it just prefers to spend it’s time on the branches unless they’re warmer.
I do not believe anyone has ever claimed that balls do not climb, it is just that there are certain people out there that are blatantly misrepresenting a flawed paper to claim that balls are a semi-arboreal species when they are not. Balls will exhibit opportunistic climbing behaviour, but they are not specialized for that life-style
Very well said!
Mine loves to climb. She will climb out of her enclosure when she’s ready to come out. It’s the strangest thing. She’s got blacked-out sides as well, and husbandry is fine. I’ve noticed as she gets older, she won’t climb if she’s still got a meal digesting.
We actually have part of a dog crate for her that she likes to climb on.