Windows 11 File History recopies unchanged files whenever its Control Panel page is opened

The repeated physical copies are the important part here. Even if opening the Control Panel page starts a check or resumes pending work, that alone wouldn’t explain another 38 GB of unchanged files being copied. Since you’ve already recreated the backup from scratch, repeating that isn’t a useful next step.

One distinction worth testing is whether File History finishes one of these additional runs successfully, or whether each attempt is stopped before it can complete. If there’s enough free space, let one additional run finish, note the completion time, then reopen the page. If it immediately duplicates the same files again, that helps rule out repeated attempts to finish an incomplete cycle.

For the report, pick one ordinary file that gets duplicated and compare the source with two backup versions. Matching SHA-256 hashes would demonstrate that the contents are identical:

Get-FileHash -Algorithm SHA256 "C:\path\example.docx"

Run the same command for each backup copy. Also record the source file’s modification time—identical contents alone don’t rule out another program changing its metadata.

Check Event Viewer > Applications and Services Logs > Microsoft > Windows > FileHistory-Engine, if present, for entries around the recorded times. Add those results and your exact Windows build from winver to the existing Feedback Hub report. That would give Microsoft a much clearer reproduction than disk usage alone. I can’t confirm that this is a known build-specific bug or that opening the page is forcing a re-index.

Until it’s resolved, use Turn off on the File History page to prevent further runs, rather than repeatedly pressing Stop, and maintain a separate backup of your important files. Keep the existing backup versions while investigating; don’t reformat the destination again.