I've got the same problem, arose recently. My yellow top has saved me on a few occasions. I've unknowingly had them stick on for a solid 7 hours more than once and come back and not have a problem starting. What else other than Kroil can I use to lubricate the switch? Thats actually what it feels it needs, the pedal returns all the way, the switch just has trouble clicking sometimes. Can I use WD40, etc?
I had this problem on my 60. Tried all the suggestions made above, but none worked. Finally looked carefully (with a light) at the brake and found a little rubber pad that is stuck onto the brake pedal arm...the pad contacts the brake switch. What I discovered is that the pad had an indent in the middle, caused by the piston on the brake switch repeatedly pushing into the rubber. The indent prevented the center piston on the switch from being fully pushed back. The pad was available from the dealer, and was pretty cheap. No problems since.
BTW, installing it was a pain until I discovered the trick. The pad has a little tail on it that you feed through a hole. Lubricate the tail (spit works) and then grab it from the back side with a pair of needle nose pliers. Pull the tail through, and the pad pops right into place. Pushing it in from the front won't work.
Had some brake work done on my 40 and when I got it back....the brake lights were staying on. Turns out the light switch wasn't clicking. Reached in a pushed the switch back and forth a few times with a flathead screwdriver they work now.
After replacing Brake Master, Clutch Master and adjusting the pedals to spec - the brake lights on my 78 would stay on. Unhooked the connector and turned the switch to adjust and it's good. In my case it seemed easier to pull the gauge panel to get to the connector/switch.
BTW - Anyone have 2 return springs on their brake pedal. Mine had 2 and what looks like only 1 spot to hook to. Can't tell if the PO put an extra spring on or if it should have 2? Can't find a detailed diagram in the manuals.