Without seeing the mechanism and inspecting for binding it is nearly impossible to say what the cause is. Do you have a slide out topper on this slide out? It could be contributing to the cause and not the slide out itself. Have a qualified technician find out the running load amperage of the motor with the slide out topper spring tension as it is and when a couple of turns are take out. 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