I've no idea about the magnet nor what's dead inside. Properly gutted as I was thinking I'd be riding it now, I only had a few little bits to tidy up. Still not sorted with bulk charging, but I was itching to get it out and could live with splitting the pack for now.
I've read the Kelly controllers are full of some brown sticky stuff so it might be difficult getting someone in the UK to repair it. Eastgem are sending a new hall sensor and magnet though. I've not popped the lid of the controller, but unless it was obvious what had blown up, I wouldn't know what I was looking for