It might be that there is something wrong with it or it has some worst case in-rush draw or perhaps the fuse was beat up by some prior load and this was the last straw. If it blows again when you’re installing or removing the load, you might try replacing the fuse with your own self-resetting fuse (circuit breaker). They sell them in the same section where the fuses are located and they plug right into the fuse socket. I put one of those on my FIL tractor that was popping conventional FB fuses due to an occassional sticky solenoid.
BTW- the self-resetting fuses referenced in the manual are service dept only due to their nature of being self-resetting. You should never have to gain access to them. By nature, they reset when the fault is corrected so they don’t need to be very accessible in the first place. Tucking them away can also discourage the novice from installing a larger capacity fuse rather than correcting the actual problem… 