None of my Dynafits (some of the same vintage) have those little nubs either. Some of the late '90's TLT's had a flat teflon circle that fit above the post that made it a tight fit when switching heels/posts, and I've had to leave them out, but I haven't seen this. I would probably Dremel the nubs off and see if the heelpiece body seats properly, but don't ask me for your money back if it doesn't work!
What does the top of the broken post look like?
