Well, you found out on your own about making sure the drive wheel is on correctly.
Next step is to find out if the drive wheel is true. If not, the band will always 'walk' and eventually fall off.
Long draw with your left hand while controlling the drive wheel with your right hand.
It's ALL in the fiber prep. You want very lofty fiber and a very loose hold on it. The fiber should be a the tip of the spindle. As you move the drive wheel clockwise, pull back on your fiber, then tension between the spindle and fiber should put twist in. as you release and turn the drive wheel slightly counter clock wise, than again clock wise, you will take the fiber off the tip, then wind onto the bobbin.
Good long draw spinning is all in the fiber prep. you want the fibers to slip by each other easily