I'm having the same problem (intermittently), when the engine is not running.
In my case, I think it may be the front master cylinder, rather than the switch. The lever doesn't always fully return, and that's when the light remains on. If I push it forward the light goes off. Engine vibration helps it to return completely, and turns off the brake light
It will be getting a fluid flush anyway, because it's a new bike to me, and I'll rebuild the master cylinder at the same time.
EDIT:
Watched the above video, and it seems that my diagnosis may be correct - master cylinder piston not fully returning.