There's always something you never considered
We had a report that a user of an Apricot PC (one of the first with 3.5" drives) was unable to insert a floppy into a drive. Our hearts sank, thinking we would lose one of our rare spare drives. The user had been carefully making backup copies of his data disks and labelling them - better than average practise.
Unfortunately he had failed to remove the older labels, and the disk was now too fat to fit through the slot.