Contax T3 Problem - Program Setting not working?

Hello.

I was hoping someone might have some experience or knowledge of a problem I have just encountered for the first time. I have recently returned from a photo project abroad and after processing 13 rolls of film shot with my Contax T3 found all the frames blank, save for the occasional frame when I switched from Program (P) to Manual (2.8, 5.6 etc)

I last used the camera in October, using the P setting and all was fine. Obviously, something has gone wrong with the P setting function, but I don't really understand why/how it could have happened?

Any advice/thoughts would be really appreciated!

Many thanks