I think it might be considered unfair towards the user recently working on it to have it finished by someone else, but if it should fail again a properly recovered work-unit might come in quite handy.
I personally feel that it would be a proper solution not to let go of eight months of computation time.
Btw: On PrimeGrid some work-units seem to have been done manually to speed-up the clean-up after some race.
Maybe sending out the remaining tasks to multiple people or have them completed outside of Boinc might be a good idea, as the results would be available sooner and, less people will be frustrated due to lost work.
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Lowend-User und Teilzeitcruncher