One or even two should not be a big deal, especially at the PVT/INST/COMM level... everyone realizes that your school/CFI could have easily had more to do with a pinkslip than any fault of yours. At CFI and beyond, the assumption is that you should know the drill, and should take responsibility for your own preparation even if your instructor(s) does not.
You want to avoid numerous pink slips, or multiple pinks on the same ride.