if you have a multimeter you can test if it has died or is behaving oddly.
It was one of the first things I tried to do but the multimeter I have here died as well. Needs a new battery. I've been watching a few electronics videos and the subject of capacitor discharge has come up a few times, good advice though, I'll remember to do that.

The capacitor feels like it has blown out, there is a definite outward pattern to the mark and a raised ridge. It does smell like electrical burn but it isn't clear to me.

What is the rating of the cap? Looks like it may be slightly dented and scuffed. Would be easy to repair that too. What’s the spec and I can take a look in the components tub, also spec of the coil too and can check
The coil is a "680" coil, so I assume it is a inductor coil like this: https://www.mouser.co.uk/ProductDeta...4bT3wBwsbAQ%3D

The capacitor is a 63V 2200uF version (CD11X). Luckily, Cytron (the maker of the ESCs) stock all these parts separately so I believe it is one of these: https://www.cytron.io/c-electrolytic...gory.discovery