@Paul Rice a similar incident happened on the first Scottish run Brian H had organised the run and I was running sweeper at the rear we were way out heading towards Mallaig zed in front of me was making some steadily getting worse noise that I could hear in the car behind him so said to Lynne reckoned he would have to stop and if so we would to to render assistance.
When he stopped we got front wheel off ( where noise from) discovered top caliper carrier missing initial decision was to remove the lower bolt and refit to top and tighten right up to stop caliper tipping onto wheel from forwards braking.
Ended up with a bit of luck after removing the other carrier bolt discovered same thread as a wheel bolt so swapped the proper carrier bolt to top and put a wheel bolt in the lower one that sufficed to keep the zed on the road rest of the weekend.
Hope you get yours sorted
Stephen.