I know this thread is somewhat dated but I've seen similar posted elsewhere. I had this problem as well and while I had the whole assembly off the bike I decided to dive a little deeper.
For those who have narrowed it down to the limit switch, which I suspect is 99% of the people posting, I got the numbers off the switch itself.
Part Number is ABJ29084
2amp, 125VAC
2 microfarad
Under the metal arm you can see the actual switch. The movement is ridiculously small, but if you're quiet you can hear if the switch actually clicks as you open and close it.
My lower limit was definitely stuck. After a liberal bath in contact cleaner and about 500 cycles with my fingers, it seems to be moving cleanly again. I was able to verify with a meter that it is opening and closing correctly now.
It's really easy to miss , but I'm including the pick of the switch assembly off the frame. You can see the switch between the mounting tab and what I assume is a guard plate
My first round of quick googling did not find that switch but I'm sure someone with more skills could cross reference it
Maybe that helps someone