MR failure point

[simplesi]

Hi, now I understand that there should be just one failure point on a MR between 3-6 set. I've had sessions where I've just hit a 4th rep but with a grind and know I wouldn't get another rep but after the brief rest I can hit another 2 or sometimes 3 so should I have lowered the weight on that set that I grinded out or as I'm doing on the next set as that could be 2 failure points?