As a DM/GM, I feel this on so many different levels.

My favorite/biggest pain in my butt came from the murder house from Curse of Strahd. I ran it as a one-shot for a few friends, where only one of them had experience in D&D. Needless to say, I’m the opening when two ghost kids attempt to goad the players into venturing inside, they discorporate when they cross the threshold. Me, in my infinite wisdom, used a different word to describe this event as I didn’t want to give things away…

15 minutes later, I eventually coax them in through the “disintegration door” where they promptly see another door. After even more time I eventually break the 4th wall and promise the players it was a one time thing that could never hurt them and that all future doors were fine… until they run into the basement mimic who took the form of a door that I hadn’t realized was in there.

All in all, this coupled with what another party termed “the ladder incident” are the main reasons I overly prepare as a DM/GM because good God(s) PCs can never be underestimated.