Looking at the pic carefully, this looks like a cronic overheating problem that is at the fail point.
The discoloration of the "b" phase fuseholder, and the fuse are usually caused by excessive heat. As the fuse clips heat-up, they get metal fatigue, and loose the spring tension, further aggravating the heating situation.
The "metal clips" are spring steel, that is factory installed on "A" & "C" phases; the piece on "b" looks like a "band-aid" fix that didn't work well.
THe fuse mfg's (Bussman) used to make a fuseholder clip retrofit for clips that had failed spring tension. I don't know if they are still available; they were OK IF you caught the tension failure early.
I would like to see the "B" fuse out of the fuseholder, to see if that's a "split" in the copper or some fancy attempt at machine work.
#104758 - 10/22/0303:09 PMRe: Fuse installed by a non-electrician!
Hotline1 Looking at the phase B fuse. It looks like they installed one end (the one not pictured) somewhat correctly. And used the tension form that knife blade to press the pictured end of the fuse onto the fuseholder terminals. It sort of looks like the blade was split, but I think there was just arcing and it made a carbon path to the blade. That would also explain why the silver end part is crooked, the black part of the fuse was able to straighten out after it overheated.
#104759 - 10/22/0303:12 PMRe: Fuse installed by a non-electrician!
to me it looks like the fuse contact was put under the socket, not in it. the thing that looks like split is the socket on top and the fuse's contact on bottom. the black line looking like the split is the shadow the holder throws on the fuse's contact.
#104760 - 10/22/0303:18 PMRe: Fuse installed by a non-electrician!
The fuse or the fuse clip are not split.The tension clip that you see is right where it is supposed to be. The fuse blade was not inserted into the fuse clip, but instead, the blade was placed below the fuse clip..The lower part of the fuse clip has darkened from overheating but it is still intact. Maybe this disconnect takes care of the lighting and the installer didn't have a flashlight with him at the time of install