Check slide out mechanism when it is extended and get under the coach where the gears and rack would stop when it is retracted. Lubricate all of this with a dry silicone spray. You can also lubricate the lock with the same dry silicone. Make certain that there is not broken teeth on the rack. Doesn't sound like the gear is an issue since it is smooth after the initial pop. There may need to be some adjustment but I would lubricate the whole mechanism first. Good luck and keep us posted.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7