While you had the basket out, did you notice if there was still water inside the balance ring on the top? If everything else has been verified, level, good centering springs, good counterbalance spring, and the tub is sitting on the base properly, then I usually find the balance ring (AP3122018) has leaked some or all of it's water and now the top of the basket shakes violently when in spin. May want to give that another look.

Well that sound about right. Something must still be loose, missing, or somewhat out of adjustment. Did anything change to start this behavior or did it just decide to do it one day? Does it walk without a load in the basket? Because I cannot look at it, I must rely on your observations and suggest a coarse of action. Based on what you are telling me you have already checked, it shouldn't be doing it. Make all your checks again, especially the springs then report back your findings.