Your product might not be dry enough.
*Correct dryness is critical, dry until the outer leaves of the flower are easily flaked off when gently rubbed.
You may have too much product in the large chamber for it to move freely. Remove some and repeat the movement. Remember the product must have room to move around for friction trimming to occur.
Product might not be cut down small enough.
Twist and tumble faster or more aggressively.
* Zippers will need lubrication or cleaning if unzipping is difficult.