It won't spin, sometimes stops mid-cycle and just quits. it can tumble, but doesn't always. sometimes i can get it to spin if i set it on the spin cycle on reduced spin, but not always. sometimes i'll try 7 times, and then give up wait and two hours later is will partially wash and then stop again mid-cycle. what could be the problem?

Washing Machines - Bosch - Nexxt Premium WFMC6400UC Front Load Washer