Iwas tightening the dummy bolt and it sheared off as I was tightening it with a hex screw driver i.e. VERY low tork.
The plastic around the bolt was to try and protect the frame to use vice grips to loosen what remained... Unfortunately I couldn't get a decent grip and the remaining part got rounded off.
The only solution was to drill it out. So using increasingly larger drill bits I tried to remove as much as possible without damaging the threads.
At this point the both was weak enough to remove with pliers, and to be sure the threads were clean I retapped them.
Crisis over...
