curiosity kicked in when I read your post, so off to Google we go, - found this;http://www.grandcanyontuberadio.com/rec ... cord_p.htm
Take a look at the 1st and 3rd pic, there is something like the piece you have, clipped onto the arm about 2/3 of the way along from the front.
What it is, what it does - I have no idea - and of course, don't even know if it's correct?
I should add, that on other pics on the web it is not shown / present? Perhaps some kind of arm-lock?
However I doubt it has anything to do with switching or linkages, it looks too flimsy. I suspect your main cam start switch issues are more likely the infamous "old Garrard grease", which over time sets pretty solid. Some dismantling and cleaning are the only cure. There are many threads on just this topic.