Unexpected rendering failure in custom SharePoint web part after recent platform updates

Hi Wilder Kimeya

Thank you for reaching out to Microsoft Q&A forum

From my perspective view, this behavior potentially aligns with recent platform-side changes in how SharePoint Online serves client assets via CDN, specifically Microsoft’s migration (June–July 2025) to a new public CDN domain public-cdn.sharepointonline.com backed by Azure Front Door. That said, if your organization enforces network allowlists, proxies, or CSP headers that haven’t been updated for the new domain or if App Catalog/CDN origins are misconfigured, some framework libraries and web part bundles may intermittently fail to load, surfacing as “missing dependencies” or SPLoaderError.loadComponentError in the console.

You can read here for more information:

https://github.com/SharePoint/sp-dev-docs/issues/10397

https://learn.microsoft.com/en-us/microsoft-365/enterprise/use-microsoft-365-cdn-with-spo?view=o365-worldwide

https://m365admin.handsontek.net/microsoft-sharepoint-online-important-update-enabling-new-public-content-delivery-network-cdn-domain/

Note: Microsoft is providing this information as a convenience to you. These sites are not controlled by Microsoft, and Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please ensure that you fully understand the risks before using any suggestions from the above link.

1/ Verify network/CSP allowlists

Ensure public-cdn.sharepointonline.com is allowed alongside the existing publiccdn.sharepointonline.com; avoid hardcoding CDN URLs in code/config. If you use SSL inspection/proxy rules, confirm they don’t block or degrade HTTP/2 asset delivery.

2/ Confirm App Catalog/CDN origin access

If bundles are hosted from the tenant App Catalog or Microsoft 365 CDN origins, make sure all users have Read access to the App Catalog and that the App Catalog origin is enabled and accessible; investigate any 403/404s in the Network tab and resolve origin/permission issues.

Link references:

https://learn.microsoft.com/en-us/microsoft-365/enterprise/use-microsoft-365-cdn-with-spo?view=o365-worldwide&viewFallbackFrom=o365%E2%80%A6

3/ Tighten SPFx dependency declarations:

In config.json and your build, explicitly declare all externals your web part relies on, and ensure consistent React/Fluent UI versions across web parts on the same page; then perform a clean ship build and redeploy:

gulp clean
gulp bundle --ship
gulp package-solution --ship

Hope my answer will help you, for any further concern, kindly let me know in the comment section.

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