I've had problems with this also.
Didn't know if it was because of installing Windows 8.1, from 8.0, or the latest versions of SyncBack Pro.
Not using Safe Copies helped somewhat.
I did notice many SBSE*.xxx files leftover here and there.
What helped the most though was:
Unchecking: Use slower but more reliable method of file change detection.
Now I rarely get an error.
Don't know why this is, but it worked.
Ted M
Didn't know if it was because of installing Windows 8.1, from 8.0, or the latest versions of SyncBack Pro.
Not using Safe Copies helped somewhat.
I did notice many SBSE*.xxx files leftover here and there.
What helped the most though was:
Unchecking: Use slower but more reliable method of file change detection.
Now I rarely get an error.
Don't know why this is, but it worked.
Ted M