Loose battery causing power reset.
On my vx-8r, when holding it a certain way and pressing keypad the battery would move enough to cause radio to turn off and back on. This is with standard battery.
I took a guess that the center connector on battery, where there is no electrical contact on the radio, is used to enable power on the other two when it is pushed in.
I put a very small piece of electrical tape on the radio where that center connector is hoping it pushes it up into battery a little more. Since doing this, it has not turned off/on from the battery being slightly loose.
Next up, is to test what the center pin is for with a meter, but so far no more radio powering off/on on it's own.