It wasn't poor build quality, it was neck problems. You'd be able to tell if your bass had this issue because your neck would be unplayable. The neck problems didn't occurr until after MM discontinued the string through body, so your bass never had this problem.
EB didn't buy MM until the mid-80's, so they'd have no input on MM basses from that era. The vast majority of basses from the problem era are fine. Most, if not all of those basses were returned for repair. Any bass that is still around now from the early-mid 80's is fine. Neck problems aren't going to appear 30 years after the fact.