happened a few times to me. The payroll people or the system can screw it up, but sometimes it can really just depend on how good your store manager/shift managers are...
If the managers are top notch they will go back and watch the tapes every Sunday before doing payroll just as a double check on punch times.
Vacation hours, PTO, overtime and working at a different stores are all the risk areas for payroll error. Keep track of everything and collect you stubs or vist myhr.cvs often.