One diaqgnostic tool I use routinely is a self-resetting circuit breaker substituted for the fuse while doing my troubleshooting. It saves a pocketful of money on fuses until the source of the short can be isolated, without the wire melting hazard created by bypassing the fuse, even temporarily. Ditto on looking for chafed insulation anywhere the wires go through a piece of sheet metal. Intermittent shorts can get downright frustrating! Is there a possibility you might be dealing with "not enough fuse"- - - -like maybe a 10 amp fuse where a 15 might be better? I've seen current loads cause repeated fuse failures where the normal current flow is within an amp or so of the current the fuse can carry safely.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!