MySQL Flexible Server 5.7 → 8.0 upgrade fails (VersionUpgradeFailed) — blocked by built-in mysql.az_replication_* procedures

The in-place major version upgrade (5.7 → 8.0) of my Azure Database for MySQL Flexible Server fails with:

VersionUpgradeFailed — An error occurred while upgrading your Azure MySQL Flexible server
from 5.7 to 8.0, please use Oracle official MySQL upgrade checker to check whether your
server is ready for upgrade.

I ran util.checkForServerUpgrade() (MySQL Shell). The only Error-level findings are 4 stored procedures in the mysql system schema:

mysql.az_replication_change_master
mysql.az_replication_change_master_with_gtid
mysql.az_replication_remove_master
mysql.az_update_replica_information

All four fail the 8.0 syntax check with unexpected token 'REPLICATION'. Their definitions contain FLUSH REPLICATION;, which is invalid in MySQL 8.0.

Key points:

• These are Azure-managed objects (DEFINER=azure_superuser@localhost), so I cannot modify them — any DDL on the mysql schema returns ERROR 1044: Access denied ... to database 'mysql'.
• Replication is not even configured (SHOW SLAVE STATUS is empty).
• They've existed unchanged since provisioning (CREATED = LAST_ALTERED = 2024-09-05);
• Every other checker finding is Warning/Notice only (utf8mb3, etc.) — not the blocker.

Question: Has anyone hit this 5.7→8.0 upgrade block caused by the built-in az_replication_* procedures? Is there a supported way to get these system procedures fixed/recreated, or is a support ticket the only path?
Target version chosen by the platform is 8.0.

Thanks!