What could be melting my main switch fuse

Hi all,

Welcome any advice on what could be burning out my 30A main switch fuse...

I'm working my way through (learning) the electrics of my 53 plate Monster 620 ie, to fix an ongoing intermittent electrical issue which

1) burns out my 30A main switch blade fuse after 30mins of riding (less if I'm using high revs), and 2) causes an infrequent 'miss' when riding... like the electrics miss a beat once in a while, causing the engine to stop firing. This happens for less than a second before it picks up again.

New stuff on the bike: reg/reg, battery, relays. New stator and fuel filters also in the post...
Wiring checked around battery; insulation looks ok, no visible breaks or shorts

I think the 30A main switch fuse protects the ignition circuit. Any clues on the culprit?

Cheers
Rob