Completion Certificates.
The usual purposes of completion certificates are to verify practical completion in terms of the contract, and/or sufficient for occupation, and/or as required for finance purposes.
If defects are later discovered, there is a potential for a claim on the basis that you approved unacceptable work.
Do not be pressured into issuing a certificate you may later have cause to regret.
Do not assume that “conditions” you attach to a certificate will later be interpreted as you intend.