There were only a couple of issues and no official line that there was a faulty batch. I'm sure it was the follower that failed, taking the pump etc. with it?
The risk with internals is you have no means to check or adjust tolerances, a lot of variables and unknowns when fitting them to a used pump, not to mention assembling them correctly and cleanly etc..... My money would be on a new LOBA unit personally. Had mine in for around 10k miles now (18 months)