Fuses can look good and still be bad. Did you test them with a multimeter? I had a similar problem on a Bally game, and it turned out to be a bad fuse that looked brand new.

Also worth a check: are the fuse housings nice and tight or are they loose? Again, this similar behavior just happened on a Williams game. When we checked the schematics to find the right fuse, we found the housing of the fuse to be just a tad loose, so sometimes it made a connection and sometimes it didn't. We tightened the housing and it fixed the issue.

Could also be a slew of other things I'm sure but here's some places to start. gl.