The original slide is pinched tight onto the ladder. IIRC, the life expectancy of the original arm was some 8-12 years. You are looking at 150+ years of wear. With that having been said, the sight at the upper end of the ladder is secured with a small screw on the bottom. If you remove it, then you can remove the slide from the ladder, pinch it tighter, check the tightness/fit, and once satisfied with the fit of the slide on the ladder, reassemble!
J.