Modern washing machines have "out of balance" protection built into the electronic control, this feature has been around for years in various forms, but in electronic controlled appliances it is more apparent to the end user. Basically, if your wash load is uneven or too heavy or too light the electronic control can sense this by a combination of motor power usuage and motor speed. If certain parameters are not met the spin cycle will be aborted. Within the electronic control a "retry" may be initiated but unless it all meets the criteria to allow spin, it just won't. Try, unloading the washer, reload and ensure a good weight distribution and have another attempt and rinse/spin or spin only.