Does this machine have a rack on the underside of the ways for driving the carriage? That sounds like there could be a tooth missing on the rack if it only happens at that point. If it was the gear, I would expect it to happen elsewhere as well.
Do your 'little red feet' all have 3 contact points, rim contact or just flat on bottom?
On my LeBlond, I turned the bolts to round to fit the VEE in the feet, as the feet have 3 contact points and conform to the floor. The rounding makes intimate contact with the vee producing self-aligning support....