There is an air reservoir (small box) on the lower left side of the outer tub with an air hose attached to it. Remove the air hose and make sure it is not gunked up and look for gunk in the reservoir. It may be that the water level pressure switch is not closing when the tub is drained out due to any restriction in the hose or reservoir.

Eric

A way to tell if this really is the problem is after the tub drains, pull the hose off the reservoir to release the air pressure which will cause the switch to close. If it still won't spin, you have other problems. If it works, try cleaning the reservoir but it' doesn't come off. A couple of methods are to use a turkey baster to squirt hot water into the reservoir fitting repeatedly or remove the hose from the pressure switch behind the control panel, try to get some hot water into the hose and blow forcefully into it to force it down into the reservoir or get a shorter hose to do the same down at the reservoir. Be very careful with the fitting on the reservoir, you don't want to break it off. If you pour water into the hose from the pressure switch, you must get all the water out of the hose before putting back in operation. The only other option is to remove the basket to get to the other side of the reservoir on the inside of the outer tub. This is a bit of work, so try the other options first.

Eric