Not only the rubber part of the heel comes loose, but also another part.
I don't have a camera to show, but I marked the place on this picture I found online, though on mine it's on the side with the zipper. It's the upper one of those two sole parts.
I mean they were cheap, but I also treated them like shit. I went to quite some parties, fell off my bicycle several times drunk one day when I wore them, I walked with them through snow and stuff. If this would be a real MMM boot, would that happen, too? I think it maily happend because they became wet.