Dualshock 3 won't stay on or charge - disconnecting/reconnecting

I'm not certain this is the best place to post this but I've been scouring the internet for hours trying to solve this.

I've used a genuine DS3 that came with my PS3 (new) with my PC for years and had no problems, but after letting it sit for a couple of weeks it will not stay connected via USB. This also means it won't charge.

If I plug it in, the usual charging flashes will happen for about 10 seconds and then it will disconnect/reconnect constantly every couple of seconds or so. The battery does not charge when this is happening.

I have tried:

• Different cables
• Different USB slots
• Using a different genuine DS3 battery that I know for sure works
• Plugging the controller in with no battery
• Taking the whole controller apart and cleaning everything
• Using the physical reset button on the controller in every conceivable manner

My other DS3 (same age) works perfectly fine with my computer and connects/charges/functions as it ought to.

I've narrowed it down to hardware, more specifically some component on the motherboard of the DS3 itself.

Has anyone else had this issue and managed to fix it? Can anyone think of somewhere more appropriate I can post this issue?

EDIT: I’ve just noticed that during the brief periods in which the controller is on, the MB gets hot and smells like burning plastic. I figure this must be related; is there anything I can do at this point?