I came close to calling off a dive once. Similar situation to Greg’s. My buddy and I were about to do a pretty aggressive dive (190’ for 25 min on 18/45). First, he had some ear problems so we went to 10’ and back about 3 times, then, on the fourth try my power inflater popped off the corrogated hose, so I had to find some tie wraps to fasten it back on. Luckily in the meantime he got his ears to start clearing, so we decided to give it one more try. We decided if one more thing, however minor and easily fixable, went wrong, that it was a sign we should thumb it, but luckily it was all aces after that.
That said, if we had been doing a "normal" dive I would never have even considered the next minor issue to be "it" and would have continued to fix any minor glitch that stood in the way of getting under way. There have been numerous times when someone had a minor issue as we were gearing up or getting in and you just wait or help fix it. Now, major problem in the middle of the dive, yeah, the dive is over, return to base. Often, though, there can still be another dive after that - fix the problem or replace the gear and get right back on that seahorse.