Home Assistant’s MariaDB app waits for its database backup lock to be acquired before letting Supervisor copy the files. Previously it reported success as soon as it requested the lock, even when a long-running operation still prevented that lock from taking effect.
The request times out after thirty seconds. If it cannot acquire the lock, the backup completes without the MariaDB app and records the failed preparation step, rather than including an unlocked copy. Tests on a Home Assistant OS installation confirmed that waiting writes resume after a failed attempt and a later backup can acquire the lock again.