WORKAROUND
1. From the Archive Manager SQL server run the following query against the ArchiveManager database:
select * from dataloader
2. Take a look at the results, and locate which DataLoaderID you would like to mark as deleted.
3. Then run:
UPDATE Dataloader SET Deleted='True' WHERE DataloaderID=X
X= The DataloaderID Of the dataloader you would like to mark as deleted.
E.g for DataloaderID 6 the query would be:
UPDATE Dataloader SET Deleted='True' WHERE DataloaderID=6