Speaking of rubber caps.....
We just recently moved into out new/old/vintage/restored home. One thing it has that I have never had is raised wood floors.
For normal washing, I have a set of Kenmore washers that we bought new in 1994 (still running). The floor in the laundry room is vinyl tile over wood, and perhaps some of the wood is not as well supported under the house in that one spot. I don't know why, but during the spin cycle of the washer, it vibrates the floor enough that the washer slowly moves across the little room!
I solved this about 90% by simply putting rubber furniture leg "coasters" under each washer foot. Dad's idea, but the sight of those rubber blocks made me think of mentioning this for others who might have the problem.
Interestingly, if you put just a little hand pressure on top of the washer it does not do it. It is right on the edge weight wise. So, when we finally retire these two and get the Neptune my wife wants, the weight of that things should cure the problem. Anything to avoid going under the house and nailing in more wood!
KP