OK, I see. But, but it's encoding control character. WinSCP expects the server to use either UTF-8 (prevalent today) or the same encoding as local Windows system. It does not support any other encoding, even those more widely used, than the one you refer to (never heard of that before).
I understand that.
I just wonder if that's some convention; or someone just done a stupid mistake of putting 0x05 into a file name.
The description of the log file means: File names that contain "Highlights" contain a x05 before "Was".
The Replace ‘\:*?’ checkbox enables automatic modification of filenames to match Windows requirements. This is not enough. Some filenames contain a x05 character that is not replaced and the Transfer failes. A x05 should be deleted (i. e. replaced by nothing).