High production these days in the automotive parts replacement field seem to have a higher percentage of parts not fitting in general.
Parts from out of the country my guess besides built for price.
Little off topic I went thru two sets of "Y" down pipes and cats for a straight six motor, first set the front "Y" 3 bolt flange was rotated 9 1/2 degrees and welded wrong. Second set the rear flange was rotated welded 9 degrees wrong, no way to mount up on the three studs per manifold. I had to cut, rotate then Tig to make fit myself. Yup like advertised "direct fit no welding".
Was told by tech my vehicle must have modified exhaust manifolds, yea right.
This is thru Magnaflow with their replacement cat system.
Both cats sent had the support bracket welded in the wrong location besides vertical vs horizontal, again my vehicle must be modified. This a 87 325is BMW factory stock.
Even big name companies can and will screw up, and lie even repeat their screw ups.
Best part I sent pictures with machinists protractors on the OEM flanges with their flanges side by side, one doesn't need but a bad eye to see a 9 degree error. Was told it could be an optical illusion.
Had to vent.

 

I hear you brother. I feel your pain. As soon as I started reading your last post. I remembered a pair of headers for an old Mustang I had. The flange had to be cut off, turned, then welded back on. I was doing the headers over a friends house. He had every tool and gadget you could imagine. He said, "Oh H#^% NO" Your not sending them back. We'll fix them. Lol... He did... Old header war stories... Aren't they great!

 

This could be a whole new thread, were not the only ones I bet.

 

Lmao. Why start a new one? Nah, Just kidding...