The bolt broke that holds the chain adj mechanism in place.
Prior bolt
I went to a hardware store that has lot's of bolts, they did not have a flange head 8mm 1.25 thd long enough, but found a just long suitable bolt.
It was 110mm, just long enough for the nylock nut to grip, ideally I'd like 115mm long to include washers also.
Replacement bolt installed
