Vintage Synth Repair

hi all,
I have the same problem a few others on here have encountered as regards replacing the internal battery and still receiving the "internal battery" error message.

In my case there doesn't appear to be any leaky capacitors or damage to the circuit board from leakage.

Any other ideas where to look/what to do if replacing the battery doesn't do the trick (i've tried a few different batteries - all brand new so it def isn't that!)
cheers
-Sam