The AA - terminal is missing, the AA pack isn't going to work without that. That AA pack also has a switch inside of it that only closes when it's in the shell and it can wear out and need to be bent a little bit to make contact again.
AA + to R22 (0ohm) to D9 to T1, after that it meets the PnC + for that pack which also looks like it's been resoldered and there could be a broken trace there.
The PnC connector looks like it has been changed, so could be broken traces there. Also check F1 (fuse) and L5 make sure neither is open.