[GeeTwo]

Can't see enough to understand clearly, but the problem has two general solutions.

First, is to provide some sort of bearing or glide or close fit (preferably without sharp corners on the leading edges) that act to prevent the rotation. The idea is to so constrain the moving part that it cannot get bound. This will require more precise machining, but usually fewer actively moving parts.

The second is to come up with some "self balancing" way to distribute the load across the piece so that it doesn't get pulled away far enough to get bound. This year on our lift, we used two chains about a foot and a half apart but driven by the same axle. We've only done a few lifts and lowers so far, but we haven't had any binding. We do need to do some more tests with off-center loads to determine how much is too much.