My dealer mentioned to me that if a slide is having difficulties moving in or out, it could be 1 of 2 common problems:
1) You may have insufficient battery power (only if you are not hooked up to shore power). The slide out motor requires a bit more power to get it started initially. If your battery(s) does not have a decent charge left on it, it may not be adequate to get the slide moving, hence your need to push on it or manipulate the motor direction quickly.
2) Your slide-out may be out of alignment slightly causing it to hang up a bit when extended. Again, causing additional resistance to the motor gearing.
Hope this helps.
'07 Rockwood 8281SS 5th Wheel
'07 Silverado 2500HD LMM Duramax Diesel / Allison 1000 CC 2LT S/B
Reese 15K 5th Wheel Hitch w/ Kwik-Slide