Power steering pump locking up

Power steering pump seems to be locking up on my 84 244, it?s the later 91+ pump. I can visually see the pulley on the pump drastically slow down, steering becomes extremely heavy and belt squeals to high heaven. Will usually happen on start up and occasionally while driving but rarely. My only idea is something is causing a clog and prevent the pump from pumping and building too much pressure, I can feel the wheel fight my inputs. Currently rebuilding a ZF rack for the car so I?m hoping that?s my problem but has anyone experienced similar?

Many pump in many cars/car brands look a lot like this:

are you using the correct oil in it? How old is that oil? Are there any metal shavings in the oil?
If parts 12 and 11 are worn i'd change the entire pump.

You can certainly try a flush. Maybe theres some solid bits getting stuck in the pump veins.

I have the final year pump with the square housing, I’ll try giving it a flush today. Got ATF in there tbh

Does your car still have a B21/B23 engine or do you have a B230? It could be a slipping balancer if it's a B230. It could also be a loose/worn out belt.

It’s a B23. The belt itself has loosened up since it was kinda burning up on the pulley so I do have to tighten it but the belts are relatively new. It only happens some days, won’t usually happen in the mornings only the afternoon when it’s warmer, it’ll squeal to high hell and if I give it the beans it’ll shutup until I try to turn the wheel then lockup again, if I keep revving and let it warmup it’ll shut up and it’ll be fine until the next start

It only starts to lock up/squeal once I try to turn the wheel