Credits use a reservation pattern. When you start a generation or edit, the cost is reserved against your balance. On success, the reservation is finalized and the credit is deducted. On failure, the reservation is released automatically. You are never charged for failed jobs.
If something goes wrong outside the automatic refund (a successful job that did not meet quality standards, for example), the support team can review the project and apply a manual credit adjustment.
Manual adjustments are determined during the issue review process. You do not need to request them separately. They are handled when a platform issue is confirmed.
Credits are not refunded for user-initiated re-runs (choosing a different camera movement, swapping the sky to a different style, upscaling to a higher resolution). Those are intentional usage.