A recipient can end up being unable to process a range deletion task if:
- The recipient persists a "pending" range deletion doc for a migration.
- The recipient fails over after cloning indexes, but before majority committing that index creation.
- On step up, the index creation gets rolled back.
- The donor marks the recipient's range deletion doc as no longer pending
- The recipient submits the range for deletion from the op observer
- The range deletion infinitely fails because the shard key index doesn't exist.
Until the range deletion task is processed, the recipient will be unable to re-receive a chunk that overlaps the range deletion task's range.