For example, some AV programs may flag & block files with certain extensions when they are being created/accessed as a "known bad file". Adding these extensions into the list will prevent them from being used as a temporary filename in future profile runs.
Create a text file called blockext.txt in the folder where the SyncBack executable is. Depending on which product is installed, these are the default locations:
C:\Program Files (x86)\2BrightSparks\SyncBackFree\
C:\Program Files (x86)\2BrightSparks\SyncBackSE\
C:\Program Files (x86)\2BrightSparks\SyncBackPro\
However, it may differ if you chose a different installation path during setup. Note that on 32-bit versions of Windows, the paths will likely be pointed to C:\Program Files\ instead.
Then add filename extensions that you DO NOT want SyncBack to use with Safe Copy filenames into this file. For example,
Do not include the period (.) before the text and only have one extension per line. Only include three-letter extensions here. Anything other than three-letter extensions like XX or XXXX will be ignored.