I almost got denied boarding for a EU -> US flight ~13 years ago because the TSA agent at the gate noticed my 2011 MBP had 2 screws missing on the bottom panel (I've opened it up a bunch of times and lost some screws in the process). It didn't convince them that I turned it on and logged in etc. They still had doubts because, apparently, missing screws on a macbook was unheard of.. in the end, they held up the plane for ~10 mins due to waiting for a go/no-go decision via phone from some decision maker at the airline (as the final call was apparently theirs to make for some reason). Luckily, they were OK with missing screws and I was let on board.