Anyone remember bsp holes? I never found a definitive answer where they came from. Was the algorithm technically flawed? Was the implementation buggy? Was it so

Anyone remember bsp holes? I never found a definitive answer where they came from. Was the algorithm technically flawed? Was the implementation buggy? Was it some shortcuts taken to speed up things, knowingly causing these glitches? Also There were so many pieces of advice out there on how to prevent them or if they occur, how to get rid of them that I was convinced at some point that half of that must have been cargo cult like.