We have had several helpers over the years terminate or be terminated before the end of the contract. They ranged from the brilliant to bloody awful/criminal. Here is some "useful advice" (and I am being sarcastic) for employers, employees can turn out to be crap or brilliant whatever checks or interviews you do. References are quite often meaningless, as in this example "child care issues" - what could be an "issue" for one person could be a positive for another.