During development on SERVER-24978 we realized there's a time between establishing cursors on mongod and establishing the merging half of the pipeline on a merging shard where the cursors aren't logically owned by anyone. We suspect that an error encountered at this specific moment would cause the cursors to be abandoned on the shards, eventually cleaned up by the cursor timeout thread, but effectively leaked.

We should investigate whether or not this is actually the case, and see if we can fix it if so.