The locks acquired here:

https://github.com/mongodb/mongo/blob/323b567d32c787eced20822f708e6e6951174714/src/mongo/db/pipeline/process_interface/shardsvr_process_interface.cpp#L97-L100

do not cover the entire lifetime of the ScopedCollectionMetadata. Thus it is possible that we are accessing the metadata after that it have been actually dropped.
We should instead access directly the routing info here that doesn't require any lock mechanism.