We are in the same boat, except that it occurs the day (today) we upgraded WHMCS from 7.5.1 to 7.8.3. @Sam you posted in July so it is safe to assume you were on current stable version WHMCS 7.7.1 or...
Hmm, thats funny i actually never tested that. It should be possible to restore. Can you test 2 scenarios for me? New space with no provisioning (so all checkboxes disabled, no domain, no nothing)...