Trailing Arm Alignment Quality Control?

[stofenism]

Hey all, long time reader first time poster and all that jazz.

Anyway, my dad's 986 had a messed up front control arm ("wish bone") and drive axles. So I decided to DIY new axles into it and replace the control arms on all 4 corners.

Everything went fine. The trailing arms in the rear looked good so I decided to reuse them. I stupidly stripped the threads on one trailing arm so I bought the cheapest replacement I could find (since I'm buying the car off my dad, my thought was that I would use a cheap one now for the next few years until I move back to the US full time and replace everything again to turn it into a track car). Normally I will not use cheap parts but I just needed 2 years of very light driving.

Anywho, since I'm not a wizard I took it in to an actual pro for the alignment portion, the car would lurch a bit to the left going over bumps at speed, indicating to me an alignment issue on the trailing arm. So the shop doing the alignment calls and says they've done everything but can't get the wheel that I did the trailing arm on in alignment.

My questions boil down to, I failed to compare the old part to the new cheap part. Could it be that the cheap part was messed up? Could I have messed something up in the installation process? I didn't compare the old part to the new one, it was the last thing I needed so once it came I put it on, lowered the car, tightened everything and drove off to the shop. Either the arm is messed up from the cheap factory, I screwed up, or the shop doesn't like DIY work. My dad trusts the shop so I'm not going down that route. Is it likely that the part was wonky from the get go?