Buds potentially fried by aftermarket charging case

Hello

I’ve had these buds for a while, and lost their charging case some time ago. I bought a replacement recently from this listing: https://www.ebay.co.uk/itm/324105240373?...

The case looked and felt just like I remember the original one, but upon inspection with a multimeter is producing voltages up to 4.5V in spikes across the charging pins to the buds while the case is plugged in, compared with a steady 1.03V while on battery.

Will this have killed the buds? if not, why else might they be completely inert now, no noise when inserted in the ear, not connecting to anything? And if so, what will I need to replace to fix this? Should I write them off and see if santa could get me another pair?

Thank you