Classic example of a stuck basket. I come across this two to three times a month.
One trick I do to get a stuck basket out is to:
1) Remove agitator, tub ring and basket drive.
2) Put machine into manual test mode.
3) Set the test on agitate.
4) As the shaft twists back and forth, pull up on the basket.
This works for me ~75% of the time. Saves my back and arms from pounding the shaft out from the bottom with the basket stuck to it.