Arcadia Glass Sliders - Need Adjustment Screws

We have a custom mid mod house (1963) with original Arcadia sliding windows and sliding doors. 
I've noticed that one of our bedroom sliding windows has a gap on top (gap is same side as the window handle/lock)  and set about learning how to adjust it. Seems there should be a screw in a bottom hole (see my photo) but when I shine a light in there, I just see a hole - no screw.
I've checked 4 of our bedroom windows and none of them seem to have this adjustment screw.
Might anyone have a dismantled sliding assembly that we can take a look at? I'd like to see what the adjustment screw looks like - length, thread, etc - and try to put one in and see if this will solve our problem. Obviously, I am running under the assumption that there weren't 99 types of adjustment screws in these things. 
https://www.flickr.com/photos/haute_pix/34555041833/in/dateposted-public/
https://www.flickr.com/photos/haute_pix/34555040543/in/dateposted-public/
Thank you!
Linda in Los Gatos
PS: Presumably ordering new wheel roller assemblies would fix the situation (http://www.swisco.com/Arcadia-Sliding-Door-Roller/pd/Patio-Glass-Door-Do...), but taking our windows out is near impossible without scaffolding set up as we're on a rather serious slope. We're looking for an easier fix!