Where this may be a real non Pekinese issue is on boom adjustable tadpole trikes.
Boom adjustment is like seat height there, and may produce a problem and cause distressing failure, when on a steep hill going to Big-big cogs.
Boom adjustment changes chain tension (duh) , but may not get noticed , as the adjustments may be incremental
and attention focused elsewhere. Easy to overlook, as Big-big combo is not used as often there, or when tweaking adjustment.