Requires odd trick to unplug

Brv-x has power on issue. Turns on fine and works normal when plugged in but dies when unplugged. Herege's the odd part, if while on and plugged in I can use my adjustable charger to reduce the incoming voltage down from 12v to 7.5v, the device continues to work and can then be unplugged. It cannot be turned on without 12v external power ( 7.5v won't turn it on, nor will just battery power) and it can't be unplugged while receiving 12v external power or it instantly cuts off altogether( 7.5vexternal is required to unplug from wall, only way to make it work…) thanks for any help you can give.