Nope, right on all counts. The bushing can cause the brake light to stay on, and there's no adjustment for the switch. Be careful moving the lever around as you can break the switch otherwise.

 

Thanks for the detail, will look into this.

 

Took the brake lever apart, the pivot pin bushing seems fine, but it does have a little play in it, is the pin supposed to slide in snug? Might order a new one anyway.
Also tried this:

Exact same symptoms I'm experiencing.
Followed his procedure but I'm not getting the pushback from the back end of the piston ram. I can't even push it in and out like he does. It does slide about 2/3mm but there is no pressure on it to push it all the way out.
Am I looking at a brake cylinder rebuild/replacement here?
Thanks.

 

Burnt out brakelight bulb of course would trigger this I think, so also start from the bulbs in the rear and trace the lines for rub till they make their connections

 

There's a spring inside that should push it all the way out to the stop. Sounds like it's sticking inside. Could be that if you take the seal out and clean the shaft of the piston it will fix it, but at that point you might as well install a rebuild kit for good measure.

There should be be red rubber grease in there to keep things lubed, sealed and corrosion free.