The issue is related to either program generation or a corrupted record.
If the data volume is low just Create a FF with the same record's which you were trying to delete but just keep the keys and make rest of columns as blank.
. Load through a custom FF upload Program which might me already existing in most of the BW systems, if not create one its simple.
The load will overwrite the record's, once its overwritten try to delete and the record will not show up again.