Fuse holders themselves on my LOTR are weak and more than one over the years have loosened up just enough to check out fine but not actually make contact with a good fuse in it. Worth a check anyways, one was my GI as well! Took way longer than I'd like to admit to find, friend actually found it...
oops, just saw the part where your fuse is actually blowing! not that probably.
Next I'd check any mods, some of them plug right into the GI.