Firstly i would find the Tag address of the value in the Protool project then find it in your S7 Program,view online through simatic Manager and establish what value is the CPU reading from your Card. If the Value is ok in your S7 project and not at the OP7 then i'd check the programming which displays this value - Incase a recent change in the code has resulted in the wrong value being written. I may be wrong but i doubt the OP7 is to blame(famous last words!)
Hope this helps
Steve