One of the problemds with blade fuses is the blade can tarnish. also (this is so old it has cobwebs on it) there is a virus among us.. In the early home computer days it bit many. but it's not a computer virus, it is a BIOLOGICAL. it likes to live on the metal surfaces used on many connectors and it likes electrical current believe it or not. Now high current (Say 3 amps from a twin 1141) will fry it. but the far lower current of the LED's may let it grow.
HOW TO FIX. In case you have not guessed.. Unplug and replace the fuse.