05 STS v8 power steering issue

My Dad's car has about 212k kms on it, pump went bad. Replaced it, that pump died and the pulley broke trying to take it off. Put in a new pump (cardone, rebuilt) and brand new gm pulley. Car works good most of the time but mid turn occasionally the power steering gives out then grabs back a second later which could be quite dangerous.

Brand new belts were put on when the pump was switched the second time (both belts)

Any idea why it might be doing this? Maybe it needs a new tensioner on the belt? (is there one?)

Thanks a bunch!