Violent Spin Cycle

Our washer has developed some violent shaking during spin cycles if there are any clothes in it (even a single piece). Aside from that the machine operates and cleans clothes normally.

I had thought that it was simply a broken suspension spring but all 4 springs are intact. Any suggestions as to what to look for next?

It turns out that the washer was no longer level. I dropped the front by 1/8" and it’s fine now.