I see thats a 100 amp fuse.... What size wire is it protecting?
I have an aversion to underfusing, and don't believe it is any safer 99% of the time, and just adds more resistance/heat than is needed in order to protect the wiring.
Try flattening the mating surfaces of that Blue seas fuse and make that aluminum appear like silver. A file is too aggressive. some 400 grit or finer sandpaper on a flat sanding block works best, especially when wet.
Trying to achieve perfectly flat with Folded sandpaper is the defintion of insanity