'Thread Error: Invalid handle (6)' errors
In very rare cases, you may experience this error being recorded (whereby the profile will likely stop with an Exception). To date, it has only been tracked to a strange error in Windows, with file-hashing enabled.
If both files are stored on a normal file system (i.e. not in the cloud, on an FTP server, etc), and are over a certain size, and are on different physical drives, then SyncBackSE/Pro reduces the hashing time by hashing the files in parallel. This means it reads both files at the same time instead of reading one file and then reading the other. In the majority of situations this is the optimal solution. However, in some rare cases it can apparently cause problems whereby Windows spontaneously raises the above error. Parallel hashing is the default mode in both Verifying (Copy/Delete settings page) and 'Slower but more reliable method of file change detection' (Compare Options settings page).
If you get errors such as Thread Error: Invalid Handle (6) then an option exists to change the hashing mode in SyncBackSE/Pro:
Modify > Expert > Copy/Delete > 'Verify that files are copied correctly' > 'Do not verify files in parallel...'
Modify > Expert > Compare Options > 'Use slower but more reliable method of file change detection' > 'Do not compare files in parallel...'
Note that this is in fact (in the code) a single central setting, so that changing one of the above settings will toggle the other. It is simply for convenience that the setting can be accessed from two different locations.
It is recommended for optimum efficiency that you do not select this option unless such an error occurs.