Probably leaking capacitors, somewhere in time.. any cure ?

[Castellen]

That op-amp looks about knackered!
Needless to say, I hope you got it replaced along with the capacitors.

Usually I use isopropyl alcohol, fibreglass brush and a solder mask touch up pen to repair any damaged green solder mask.

I've written a bunch of documentation you might find useful:
http://amiga.serveftp.net/hardware_repair.html

[Castellen]

I'm really impressed that it's still working! :-o
You should probably get it looked at if you want it to last much longer though.  The electrolyte leaking from the capacitors will be damaging the PCB's tracks and vias.

Let me know if you want an estimate for repair and the currency you use.