1. “This record is locked. If you need to edit it, contact your admin” exception will be thrown when someone tries to edit a record which is locked via Approval Process.

2. If you are facing this issue while viewing the record, then subscribe to the following known issue

https://trailblazer.salesforce.com/issues_view?id=a1p3A000000mDW0QAM&title=locked-lead-records-via-an-approval-process-prevents-the-lead-owner-from-viewing-record-in-lighting-if-they-have-not-viewed-the-record-prior-to-lock

3. If you have deactivated the approval process, make sure the pending requests are removed.

https://help.salesforce.com/s/articleView?id=sf.data_approval_requests_remove.htm&type=5