Developing Problems, maybe with JOBO developing tank?

I have been developing my own bw film for some time, so far in a Patterson tank and without problems. Recently, I got a used JOBO-2236 Club tank…I have used it a bit, but I have gotten far more development issues (uneven development etc) with the JOBO tank then I ever got in the Patterson. Strangely, when developing two rolls in the JOBO, often only one roll is affected.
Does anyone have a clue what could cause this? Can a tank (which is light-tight) have some other problems? Can the Spools have a problem?

Or does anyone have an idea what could have caused this?

I attached a sample, the photos were taken on a 120 roll of Rollei RPX25 and developed in Rodinal 1:50 for 11 minutes. All my previously shot RPX25 (developed in Paterson) looked great…interestingly, the second roll of RPX25 in the same developing process is more or less fine.
The problems on Pancro 400 in my other post are also in this tank…

Thanks!

Unedited Scan:

Converted pictures: