The call to findIntersectingChunkWithSimpleCollation is being called with the original shard key after a refineShardKey operation. This results in a ShardKeyNotFound exception being thrown which goes unhandled.

This should have been addressed by the changes in https://jira.mongodb.org/browse/SERVER-48365 by making sure that the migration recovery entries are written while holding the dist lock. However, there is an interleaving where this is not the case.