If your slx is really hard to extend, Take the pole sections apart and run your finger along the inside edge of the clamp that butts up to the inner edge of the carbon pole. If you find the inner clamp edge is higher then the carbon section.Thats were your problem is.
File or sand the clamp edge only untill its level with the carbon,Rub your finger over the edge to check, when done Apply a bit of polish and the pole sections will slide and glide far better.
Neil