If I'm not mistaken, a couple of guys in Kern Dog's thread said there was a bad batch of PST arms that weren't jigged up correctly. I don't know if PST offered replacements or refunds, but that train has set sail.
Honestly if you know the date you purchased your PST UCA's it can't hurt to call them. I know they sold to Kanter but there should be some record of that bad batch, and if you could confirm your UCA's were part of it at least you'd know the issue.
Otherwise you might need to get ahold of a known good right UCA to compare to. If you don't and just buy new UCA's you run the risk of just throwing more parts and money at a chassis issue. Even if the UCA is the more likely culprit, it's still a risk.