Have you looked at each of the three expressions individually and tried to see if one of them is acting weird or if all of them seem incorrect? The problem is that from the looks of it, your expression looks right. I don't see any issue with them. So unless I have a sample to look at, I will only be able to guide you and not provide anything concrete.
One thing you can check is if your set analysis is in the same format as HIRE DATE? May be add this to a text box object -> =AddMonths(MonthStart(Today()),-13) and see if it is in the same format as HIRE DATE or not. If it isn't then add a Date() function with the matching format in all your set analysis