Ok since no one else is chiming in...I’ll give it another go.
Looking at the pics his nose looks really damaged. And barbels all missing. Did you get him like that?
How many times has he been “sick” and recovered?
If I’m right in my theory, this is due to jumping. Would explain the missing barbels, going vertical, and being able to recover from it. If it’s due to jumping then just find out what’s causing him to jump and eliminate the problem. Mine jumps when there’s food left over on top...when really hungry he’ll jump out and try to intercept the food and sometimes will get the top.