On mine, one of the tiny two hole balun transformers in the RX chain appears to have been the source of something corrosive that oozed out and dissolved the vias. This was around the IF cans. What I saw under the microscope were slightly greenish crystals growing out of the vias - most obvious from below.
It turned out to be fixable.
The FM path diverges in the IF, so seeing if FM also has no signal tells you how far along the RX the fault is.
