Hi Adam
It looks like a clutch/brake problem. The clutch isn't releasing drive to the basket for wash. It might simply not be fully braked - it relies on the drum still spinning a bit when the brake engages. It must be still spinning a bit to ensure that when the brake is applied to the drum, the clutch pawl releases the clutch. If for any reason such as a power cut the spinner slowed to a stop without being braked, the clutch won't release properly.
First, try this...
1. Set the timer to spin. 2.Allow it to get up to full spin speed. 3.Open the lid and the brake should engage immediately. You should hear a loud clunk as the brake engages, if all is working right, once the drum has braked to a stop, you can try a wash and see if it behaves now. If it is now OK, it just hadn't braked properly.
Otherwise you may need to dismantle the belt, pulley and clutch assembly and check it over. The clutch spring can get mangled and not release properly.
the other thing to check is operation of the spin solenoid.