Replying to Box Question

I built a 2 by 16 foot funbox, covered it with hdpe, and was sessioning it the past few days. when i hit it with my armada ar6's (only used 2 days) it seemed really sticky, which was weird because i just waxed the skis.  but when i hit it with my public enemy's (beat up, not waxed recently, used like 4 days this year and a ton last year) it slid perfectly.  it doesn't have coping on it, but if it slides this well i don't think i will need coping. does anyone know why this might have happened. Also, the weather was warmer on the day when it slid nicely, but only like 5 degrees Fahrenheit warmer so i dont think that is the problem. input would be appreciated! thanks!