Mine did the same thing! It was only loose! I had to get everything from the seal forward new and any longer running it would have needed a new crank I think. I will tourqe it to spec and it will be new but I don't want to take the chance of it happening again. I will say the bolt I took out was the new design but some slug used a standard "hardware store" washer and I believe that had some bearing on my problem.
After reading all the threads I have on this one simple bolt I have never heard anyone come back and say that their new design bolt has several thousand miles of trouble free use! That is good news!