Yes, I have also. I was told that it would not felt due to the fact that there is not supposed to be any agitation. Well, I put a wool shawl in that kitty had barfed all over and set it for cold water, ulta gentle cycle. Whoops, instant felted shawl!
Since then I had felted things (on purpose) and it works fine. I would suggest doing a test swatch and put it through the washer to see what happens.