how to fix a tricity wdr1020 washer dryer?

on drying cycle, pump starts and empties any water from drum, drum rotates 2/3 times and pump repeats.
then dryer program starts, fan with heat. drum rotates for 2/3 turns but then Stops rotating ... the fan and heat continue to run.
the drum gets so hot the stat cuts out the heat(after about 5mins) . fan continues to run
what controls the on/off of the drum rotation and how do i repair it