I had a Rottendog WPC95 power driver board on my NBAFB. With this board everything else worked fine except the shot clock, which was showing just random numbers or just flickered some nonsense. The board was measured, one IC-chip replaced, wiring measured, shot clock replaced, but with no avail.
When an original Williams board was installed, everything was working just fine. In some other WPC95-game the very same Rottendog board worked flawlessly. So go figure