RemoveShard code collects information about collections to calculate remaining amount of bytes to move. It uses collstat to do this. Though we filter for collections when we get the namespaces on the shard, there is a chance that by the time we run the collstat, the user dropped the collection and recreated a view with the same name instead. In this case the collstat (and remove shard / shardDrainingStatus) fails. However it is safe to swallow this exception.