This behavior is commonly tied to how the Photos app indexes folders and builds the filmstrip, rather than strictly following the current File Explorer order.
Since repair, reset, and changing File Explorer sort order were already tried, use these checks instead:
- Make sure the folder is added to Photos as a source.
- In Photos, open Settings.
- Under Sources, add the folder that contains the affected pictures.
- In the newer Photos app, photos from other locations can also be added from Gallery > Add folder.
- Expected result: once the folder is indexed by Photos, the navigation arrows and filmstrip should include the full folder contents more consistently.
- Rebuild the Windows search index.
- Go to Settings > Privacy & security > Searching Windows.
- Open Advanced indexing options > Advanced > Rebuild.
- This can help when some folders work correctly but others show missing, repeated, or out-of-order items.
- Check whether the affected folders are optimized as picture folders.
- In File Explorer, right-click the affected folder > Properties > Customize.
- Set Optimize this folder for to Pictures.
- Apply the change.
- Check photo metadata consistency in folders that fail.
- Problems that happen only in certain folders, especially when photos come from different devices, can be caused by differences in Date taken metadata.
- In File Explorer, open the folder, switch to Details view if needed, and review the Date taken field.
- For a test, open a sample image in Photos, right-click it, select File info, and edit the date/time so a few files from different devices match the expected sequence.
- If the folder is only meant to appear in the app and not be managed there, remove and re-add it.
- In the newer Photos app, remove the folder from the left navigation area, then add it again.
- In Photos Legacy, remove the folder from Settings > Sources, then add it back.
- Removing a folder from Photos does not delete the folder contents from Windows.
- If the files are in OneDrive, verify the order there separately.
- In OneDrive on the web, sorting applies in My files folders, but not in Photo view, which aggregates photos from multiple locations.
- If the issue appears only in a photo-style aggregated view, check the actual folder instead.
If the issue is limited to folders that mix photos from different cameras or phones, the strongest match is inconsistent indexing or Date taken metadata in those files. In that case, rebuilding the index and testing a few files’ metadata is the most relevant next step.
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