John There are roller bearings at the bottom of the mechanism. Those are likely worn to flat spots that now mostly just allow the parallel arms to slide rather than roll through the horizontal channel. Sparky’s were worn almost to flat spots. Someone here, I believe, suggested replacing the rollers with hardware store plastic like patio door screen rollers. That was done and along with scrubbing clean and lubrication the mechanisms function smooth and easy.
Last edited by 46Sparky; 06/16/20262:09 PM. Reason: Photo added
