1.11.0 → 1.9.1
I don't know that this is a bug with jQuery UI slider. The slide event continues to fire even if false is returned to the previous slide event. This allows the user to be able to slide the handle backwards after the slide event returned false.
I think the problem is really with the code that decides if to return false or not. Handles are not dragged at a 1 point intervals. It depends on how fast the mouse moves. If the mouse moves really quick then the values can jump past the 50 point difference.
First slide event the values are [ 47, 100 ], set rangevalue = 53, return true
Second slide event values are [ 52, 100 ], don't set rangevalue, return false
This results in what looks like the values getting "stuck" but they really are not. You just stopped setting rangevalue to early.
Check out this example, the top slider has "fixed" logic to always make sure that the difference between the 2 handles is always stopped at 50 and the bottom is the original logic.