Handle too hard to turn?
A: There may not be enough slack in the yarn between the skein and the machine.
To fix: Unravel more yarn from the skein.
B: Yarn may be jamming in either tension arm or needles.
To fix: Remove yarn from tension arm or needles.
Missing stitches? Knitting too loose?
You need more back tension.
To fix: Wind more turns on tension arm to suit.
Sharp snapping noise?
Too much tension.
To fix: Re-thread yarn through tension arm. If it is still too tight, leave one or more turns off the tension arm.
Tension arm fallen off?
On some models of the machine the tension arm is designed to slip off.
To fix: Snap the tension arm back into place.