Yes, the LLC should file an amended Form 1065 to correct the errors. Since the K-1s were marked as final by mistake, and there were missing codes for lines 14a and 19a, it's important to correct these issues to ensure accurate reporting for the partners. When amending, make sure to check the "Amended Return" box on Form 1065 and provide the corrected K-1s to each partner. This will help maintain accurate tax records and ensure compliance with IRS requirements.