Some thumbnail images appearing as broken in Microsoft List

Question

Hello,

Recently, some image thumbnails are appearing as broken in my Microsoft List. Many of the recent photos (roughly top 100) added appear as they should within the list but as I scroll down, the thumbnails become broken. When I click on the broken thumbnails, the correct image does open properly.

I have tried clearing the cache, opening in Chrome instead of Edge, opening in private window none of those resolve the issue. In developer, it is throwing a 400 error when trying to get the images and an error: 'Microsoft.SharePoint.Client.ClientServiceException'. I confirmed that all broken images appear in the site library.

None of the images are large files and mainly .png with some .jpg (does not appear to matter). I don't know how to further try to resolve this.

Thanks

Answer 1

Hi @Andrew Gravelle,

Thank you for reaching out to Microsoft Q&A Forum.

This issue occurs when Microsoft Lists is unable to generate thumbnail previews even though the full images still exist and open correctly, which means the problem is with thumbnail retrieval, not the files themselves. Since the top ~100 images load but older ones fail with a 400 error and a Microsoft.SharePoint.Client.ClientServiceException, it suggests that SharePoint’s thumbnail API is intermittently failing, often due to indexing delays, corrupted thumbnail cache entries, or an internal service bug affecting how Lists requests preview renditions. Your tests (clearing browser cache, trying different browsers, private mode, and verifying the files exist in the library) rule out local browser-level issues, further pointing to a backend SharePoint rendering or throttling issue. In most cases, this type of behavior resolves after SharePoint completes reindexing or after Microsoft deploys a service-side fix, but if it persists, reindexing the affected library or opening a support ticket is typically required.

 

Given the nature of the problem, the most effective next step is reaching out to your IT admin and ask them to use their admin credentials to submit a support request through the Microsoft 365 Admin Center.

 

Microsoft also provides customer service phone numbers based on your region. You can find the appropriate contact number here: Customer service phone numbers - Microsoft Support  This route ensures that a Microsoft support engineer can initiate a remote session to investigate backend configurations, run advanced diagnostic tools, and, if necessary, escalate the case to specialized teams with access to internal systems and logs. These backend resources are essential for resolving issues that go beyond what’s visible in the user interface.

As community moderators, we’re here to guide you, but due to privacy and security limitations, we don’t have access to the backend tools required for a full resolution. For this reason, contacting Microsoft Support via the Admin Center is the most secure and efficient way forward.

 

I hope this helps you resolve the issue quickly. I’m glad to assist and truly hope the information provided has been useful. Please feel free to reach out anytime if you need further assistance.  

If you find my post helpful, kindly consider marking it as the accepted answer. Doing so can assist others in the community who may have similar questions in finding solutions more quickly.  

Thank you for your kindness and contributions to the forum. 

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Answer 2

The issue you're experiencing with broken thumbnail images in your Microsoft List could be related to several factors. Since you mentioned that the images open correctly when clicked, it suggests that the files themselves are not corrupted. Here are a few things to consider:

1. Browser Cache: Although you have already cleared the cache, ensure that you are also clearing any stored data related to the specific site.
2. Image Size: While you mentioned that the images are not large files, ensure that none exceed the limits set by SharePoint, which can affect thumbnail generation. For reference, images larger than 50 megapixels can cause issues in picture libraries.
3. Permissions: Sometimes, permissions issues can lead to images not displaying correctly. Ensure that your permissions are set correctly for the images in the library.
4. SharePoint Service Issues: The error message you received (Microsoft.SharePoint.Client.ClientServiceException) may indicate a temporary issue with SharePoint services. Checking the service health dashboard for any ongoing issues might provide insights.
5. Developer Tools: Since you are seeing a 400 error in the developer console, this could indicate a bad request. It may be beneficial to check the network tab in the developer tools to see if there are any specific requests failing when trying to load the thumbnails.

If the problem persists after these checks, consider reaching out to Microsoft support for further assistance, providing them with the error details and any relevant timestamps.

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References:

• Common issues syncing Microsoft SharePoint lists offline
• 403 Forbidden error on OneDrive or SharePoint
• SharePoint Online Picture Library doesn't display thumbnail previews
• Contacting support
• Work with photos in a picture library
• Switch the default for document libraries from new or classic
• Browse resource files sorted by file name in the Page tab of the Sources tool