Environment
macOS Sequoia backing up to a Synology NAS over SMB.
What happens
The menu bar says Preparing backup for hours without transferring data.
What I have tried
Restarted the Mac and NAS and confirmed that the backup share has free space.
I would appreciate advice on how to identify the root cause without risking existing data or configuration.
Verified community troubleshooting
This looks less like a hardware failure and more like a configuration issue.
Likely cause: A stale in-progress snapshot or damaged backup state prevents a new incremental scan.
What I would try: Remove the stale in-progress bundle, run tmutil thinlocalsnapshots and reconnect the Time Machine destination.
Keep an eye on the relevant logs during the test; they should confirm whether the hypothesis is correct.
Good point about changing one thing at a time. I had been testing several settings together.
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