How to resolve 'SnapshotInProgressContainer - Structure missing' and 'Structure has wrong type' Time Machine errors on macOS 26.1?

Question

Level 1

8 points

How to resolve 'SnapshotInProgressContainer - Structure missing' and 'Structure has wrong type' Time Machine errors on macOS 26.1?

Narrative:

I've noticed the errors below on macOs 26.1, they may have shown up on an earlier version, I don't know. I've tried erasing the external disk and have since done a full backup which succeeded, according to Settings/General/Time Machine, but the errors persist.

Questions

Are the errors below significant? If yes, what action is needed?

Time Machine related errors of concern:

Error Domain=TMStructureErrorDomain Code=4 "SnapshotInProgressContainer - Structure missing"

Error Domain=TMStructureErrorDomain Code=7 "Structure has wrong type"

Config:

macOs 26.1

Mac Studio - Apple M1 Max

2TB external Timemachine backup disk: Media name : Seagate GoFlex Desk Media

More complete log segment.log

[Re-Titled by Moderator]

Original Title: Time Machine reports structure errors on macOS 26.1 - Error Domain=TMStructureErrorDomain Code=4 "SnapshotInProgressContainer - Structure missing"

Mac Studio, macOS 26.1

Posted on Nov 23, 2025 4:35 AM

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Answer 1

Nov 23, 2025 6:57 AM in response to RedPike

and what are doing... ie what generates the error?

Shown up where?

What is the bigger issue?

Did you erase/reformat/initilize this drive as new when you first bought it— to remove any proprietary software pre-installed— this get you back to terra firma...(?)

ref: Erase and reformat a storage device in Disk Utility on Mac - Apple Support

ref: The "Snapshot In Progress Container" message on Apple systems refers to a temporary state during Time Machine backup or macOS update processes

classic error messages when a drive is working in a state of failure as follows:

Time Machine has completed a new backup for you

can't create the backup

failed to complete the backup

an error occurred while preparing the backup

If you continue to get these errors I would suspect the Time Machine drive is starting to fail, the answer would be replace the drive and /or try another drive and compare your results..

Trouble Shooting Time Machine —use Disk Utility.app>First Aid to Repair Disk

Time Machine troubleshooting on Mac - Apple Support

Uninstall all third party apps that are Cleaners/Optimizers/VPN/Anti-Virus

all known to cause issues on the macOS

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Answer 2

RedPike Author

Level 1

8 points

Nov 23, 2025 7:29 AM in response to leroydouglas

Hello

Thanks for your response.

Your question: "and what are doing... ie what generates the error? Shown up where?"

Running backups cause the errors to show up in the log stream, using

#!/bin/sh

log stream --style syslog --predicate 'senderImagePath contains[cd] "TimeMachine"' --info

Your question: "What is the bigger issue?"

Backups appear to be working according to System Settings. I'm just concerned that these errors might point to a failing disk.

Yesterday I successfully health checked the external device using Disk Utility. The disk was reformatted using your ref above. Then it was added to Time Machine and an initial backup was apparently successfully completed.

Following the troubleshooting guide I then clicked on Verify your backup disk but could not see the 'Verify Backups' options on the Time Machine menu-bar menu while holding down the Options key.

I have no third party apps that are Cleaners/Optimizers/VPN/Anti-Virus

Cheers

J.

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