When i went to use my slt 2 the other day the rear spool didn't want to spin. I gave it a little turn but nothing. It took a few goes to get it going and then it was fine.
The belt is fine but i cant seem to see anything wrong. Everything is lubricated as it should be.

Is it a fabric or rubber belt? If it is fabric then you may need to increase the tension on the rear wheel. On the reel takeup arm there should be a screw on the bottom. Make sure the spring is in good condition then rotate the screw counter-clockwise to increase the tension. If the belt has gotten too slick over time then you may need to replace it. Easy fix though, take it off and flip it over before putting it back on.