If you claimed excess social security withholding or FICA, and it did not actually apply, and the IRS actually released your full refund as shown on your tax return for that year, you should amend your tax return.
Rule: If you have more than one employer, more than one W-2, then it's possible you do have excess FICA. When there are two or more employers it is the only time this can happen.
The fact that each employer did withhold 6.2% would be correct. The problem, for you, occurs when the total earnings between the employers is greater than a certain amount. For 2020, that amount is $137,700 (total social security tax of $8,537.40).
When this occurs, then you have a right to receive a refund of the difference because both employers paid what that were required to pay to the IRS.
Amending your return can be completed by using the instructions provided in the link below. Be sure to read carefully before you begin.