BA II Plus Malfunctions

My BAII plus has been acting weird recently (i.e.: incorrectly computing PV,FV, PMT). I changed the battery, rebooted to no avail. My spare BAII on the other hand is doing fine. Anybody experienced this before and is there a fail proof way of ensuring all functions are working without having to resort to triple checking your cash flow calculations on the exam or buying a new calculator on June 6th Tx,

Is PY/CY set to 1?