Possible data loss: Update mode reports 0 files to update, but Mirror detects missing files (Android MTP)

[Hello]

Hello Zenju,

I would like to report a possible issue that may lead to data loss.

Environment:
- FreeFileSync 14.10 (latest)
- Windows 11
- Android phone connected via USB in File Transfer (MTP) mode
- Destination: USB flash drive

What happened:

I synchronized my Android phone to a USB flash drive using the Update sync variant.

The synchronization completed successfully without any errors or warnings.

Immediately after that, I ran Compare again using Update.

FreeFileSync reported "0 files to update", so it appeared that the backup was complete.

Fortunately, before deleting the data from my phone, I manually checked the USB flash drive.

I discovered that many files had never been copied, especially:
- ZIP files
- Many files from the DCIM/Camera folder

Then I changed only the sync variant from Update to Mirror.

I did not change the source or destination.

Mirror immediately detected and copied all those missing files.

This is the concerning part:

Update Compare reported "0 files to update", while Mirror immediately found many files that were actually missing.

If I had trusted the Update comparison result, I would have deleted the files from my phone and permanently lost my data.

I don't know whether this is caused by Android MTP limitations or by the Update comparison logic.

However, from a user's perspective, this behavior is dangerous because Update reports that the backup is complete while files are actually missing.

Could you please explain whether this is expected behavior or a bug?

Thank you.

[xCSxXenon]

When using the "Update" method, do you have the box checked to use a database file to detect changes?