I found my first bad splice at the same time I found out there WERE splices--in about 72-73, on a friend's 68 383 RR. The ammeter had been bouncing around, and at some point--in his apartment parking lot--we had the dash apart and the harness pulled out. He was beginning to think I was NUTS. "I" was beginning to think I was nuts!!! and then I found it!!. Stripped it back soldered it all together
In my lifetime, I've become aware or found maybe 10 or a dozen bad splices. They are surely very rare to give problems. I would guess that the ones went bad were never "that good" to start with