As I remember it, the three biggest problems were:
1. that cardpunch machines were totally unforgiving - if you made a typo, you started over with a new card, and
2. the card decks (programs) had to stay in exact order - easy to do, but DON'T drop them! - and they were not the slightest bit inclined to STAY in order unless you were ever-vigilant with them, and
3. that the card READER machines were often referred to as the 'card-mangler' machines so, even if YOU did everything right, the card-reader could STILL do your program in!
I heard a horror story regarding that very thing! The guy has been in IT for 30 years. He said he had worked for days(I think). He was getting ready to put his work to use and dropped the cards. He said for a brief moment he contemplated suicide lol. He told me after that he numbered his cards with a pen.