Electrical Problem Qingqi Pioneer XF200-2V

Hi.

My bike came to a standstill recently caused by a short circuit which blows the fuse, even when the bike is switched off.

I tried wiring a headlamp bulb in place of the fuse and unplugged the connectors around the bike.
The only time the bulb goes out is when I disconnect the stator coil, then the bike starts as normal.
I got a replacement stator but the problem still existed
I eventually found the fault.
The rectifier has shorted to earth.
Does anybody know the cause of this fault?
Do these rectifier units have a limited lifespan?
It's a 2006 model.

Thanks

Jim Welsh