The instance of poor quality converter rebuilds is not a new one.
Proper jigs and fixtures are the key to producing quality parts...

When you get the converter out.....IF you can get access to a lathe that can swing it....grab the converter by the hub and gently clamp it..

Rotate the converter slowly by hand and observe the pilot on the front of the converter.

Also watch the entire outer rim of the converter for run out.

Before installing the replacement.....check it for run out as well

This sort of crap just sucks....

What brand of rebuilt .?????????

Rebuilt converters do not always get a fresh hub welded on.....If the hub surface is good they get used again.

So it's a crap shoot.