I'm thinking it could have been caused by a loose electric terminal, & creates enough electrical resistance to cause excessive heat & melted that terminal. Or maybe its possible that the load wire/positive wire had excessive amperage draw & melted that terminal.
Thanks for the Pic - frankly the Blades/Connector looks very decent.
If it wss me - what I would do - With the battery off the bike - and preferably on the garage floor or similar - plugging the charger into the wall 1st - then when charger light goes steady - what happens that 1st moment/secs when you plug charger into the battery ? If it kills the charger - unplug Charger from Battery Immediately then unplug charger from the wall. Does the Charger start charge cycle with normal charging indicator light ? If it does please monitor charger heat and battery heat with your palm to detect any Hot/Hot overheatiing.
Someone replied from a user's group with the following:
It's the original levels battery design. They used an off the shelf battery case and cradle that had pins that were too short and too thin for the battery. They used a better cradle with longer thicker pins in later model level 1s to fix it. It's not user error on these models it should have really been a recall.