Problem with my Horseman LE rail

The front standard tightening mechanism for the "swing" movement on my LE will not lock or I guess a better description is that it will not tighten. I knew that it was starting to feel weak, but today I was out and it finally gave up. I can use it but while fiddling with "rise" or "tilt" I am inadvertantly swinging it a few millmeters without meaning to.

Are they're any owners of 4x5 Horseman LE rail that can tell me how easily or how difficult this is to fix?

Thanks
Chuck