Copied from the other thread.
Not to many people seem to have this problems but when I try and replicate it it is because something isn’t “balanced” I guess is a good way to word it. I would say loosen up all the tension bolts including the 4 long ones and as you start to snug things up check the rails with a carpenters square, if don’t have one they are about $5 at the hardware store. This is how I have been checking on the new middle assemblies I have been making. If they aren’t square when it is completely loose something else is wrong, either with the rails being bent or your roller f’s are tweaked. The roller f are very strong and should hold it very square by themselves.