Could it be that the power steering system is contaminated and keeps putting garbage in the fluid? As soon as enough debris accumulates in a small orifice then problems begin?
Even if thoroughly flushed there could be a hose or hoses that are the culprit. Is it possible they’re shedding some junk from inside?
I’d be asking lots of questions after the second rack was replaced, more questions after the third, and asking for the help of a psychologist or a much better automobile diagnostician.
It wouldn’t hurt to drain the system one more time and send a fluid sample off to Blackstone Lab or another lab or simply replace all hoses and components that could degrade.
I mentioned before… isn’t there a term that describes somebody who repeats the same action over and over, expecting different results each time?
CSA