My buddy has 52" 112 Fortrex, The adapter ring on the prop breaks of perfectly. This has happened to two of them. This a new one for me. It broke so cleanly I was going to just epoxy them back together. I have not seen this, and even google search came up empty. The only thought I have as the cause is the prop shaft is set a tad to deep putting flex pressure on the ring. But there is no signs o.f rubbing so that theory doesn't really hold water