Originally Posted by
Road Fan
What about chainring and sprocket not in-plane, I.e. chain line not matched front and rear? Combined with a chainring wobble?
As they tell medical students, "when you hear hoofbeats, think horses, not zebras".
Slack chains on coaster brake bikes as very common. Add to that the fact that she was able to work the chain back on.
So, while there were other possibilities, it made sense to start with the likeliest before looking for the zebras.
As it turned out, that's what it was.