How to remove it from DB (before doing that, shut down SDDC manager and take cold snapshot, so you will have temporary backup just in case) 

manually clean-up the DB entries:


psql -h localhost -U postgres -d platform -c "truncate vrslcm;"
psql -h localhost -U postgres -d platform -c "delete from vm_and_vm_type_and_domain where vm_type ='VRSLCM';"
psql -h localhost -U postgres -d platform -c "delete from credentialhistory where credential_id in (select id from credential where entitytype ='VRSLCM');"
psql -h localhost -U postgres -d platform -c "delete from credential where entitytype ='VRSLCM';"