The Center director may review transactions for correctness, and take appropriate action under his general authority to correct errors, including those in appraisement where appropriate, at the time of:
(a) Liquidation of an entry;
(b) Voluntary reliquidation completed within 90 days after liquidation;
(c) Voluntary correction of an exaction within 90 days after the exaction was made;
(d) Reliquidation made pursuant to a valid protest covering the particular merchandise as to which a change is in order; or
(e) Modification, pursuant to a valid protest, of a transaction or decision which is neither a liquidation or reliquidation.