Don't discount dry joints, solder connections.
Basically, dry joints are where the solder has not created a good contact between component and circuit board. Age only exacerbates the situation.
Vehicle electronics are full of mediocre quality components that can seriously suffer with age. I've had anomalies on both my ur and v8. In the V8, a few things have randomly been fussy while warming up.
A good quality soldering iron (butane) can be had fairly cheaply, along with solder and flux.
