From what he says the fuse isn't blowing so its not over current. It points to a connection issue causing heat build up over time at which point the heat melts the plastic fuse holder and the resistance is so high that not enough voltage can flow.
I just did a quick google and this article illustrates what I think is the problem:-
https://www.redarc.com.au/faq-tech-t...d-fuse-holders
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