Took me several hours to trace an intermittent fault on a Vero creation recently. Magnifying glass out inspecting for any little shorts between tracks. Flexing the board I could induce the fault. Now are all the legs of the IC I had to change making good contact? Yes!
Eventually I spotted that a naked ground wire on the non-track side was able to contact a little monitor wire I had soldered from the track side because it protruded onto the ground.
Peter