I believe the out-of-balance spin sensor is not as efficient as the manufacturers claim.
I had an AEG from 1998, in which I washed synthetic fibre pillows. The machine passed through the cycle okay, until the final spin. The drum was rotating slowly (measuring the degree of out-of-balance), then with a TERRIFIC jump, it leapt into spin. There was a horrible scraping sound, and I pulled the plug.
It turned out that the whole tub assembly jumped vertically, causing the drum lip to gouge a score/groove in the bottom of the door glass.
I suspect that that particular incident, contributed to the drum bearing failure a couple of years later. :-/