Unfortunately it is common to blow the fuse like that. The other caveat is to make sure you let the jack stop moving before switching directions. I would hitch the trailer up and then figure out how to disassemble inspect and grease the jack.
And most importantly, always make sure your body especially your feet are clear of the trailer when using the jack in case it fails and falls. If it falls it will come down faster than you can react, as in it will be on the ground before you even realize it failed and fell. You don't want your body parts anywhere near that impact point.
No on the 40 amp fuse, but you can replace the 30 amp with a 30 amp automatically resetting circuit breaker from the auto parts store.
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