Avos are lovely instruments, but challenging to fix, in my experience.
I bought one of mine s/h, not working quite right. Fault was easily traced to a weak contact in one of the leaf switch assemblies, specifically a contact that is meant to “shunt” the zero ohms knob, when not reading resistance. The factory service manual, of which I have a copy, sanctions simple retensioning of the leafs with “duck bill” pliers. Trouble is, I need to get access first, and three years on I have yet to pluck up the courage for what looks like a marathon of desoldering and resoldering fragile old wires.
Another caution in the factory manual is, during disassembly, using a piece of non magnetic material to shield the movement magnets, avoiding contact with screwdrivers. I guess the screwdriver might otherwise become slightly magnetised and, in turn the movement would become slightly demagnetised, throwing it out of calibration. I’d not have thought of that, and wonder how many other things I might not have thought of.