If the source files are on a NAS, that popup wouldn’t be triggered by anything being done to the source files. Image Guardian only protects backup files that reside on local NTFS volumes, not files on network shares. (And if the Archive bit is actually being cleared, then that means Image Guardian didn’t block it, in which case that's not the operation it reported blocking.
) The log mentions that it blocked access to a file on Harddiskvolume3, which would refer to local storage. So what’s probably happening is that Image Guardian is active on your TARGET device, since that’s a USB drive. Image Guardian won’t stop you from copying new Reflect backups to a protected volume, but it will prevent any further modifications to those files immediately after they’re created on the volume.
So yes, it's possible that the application you're using is setting off Image Guardian because it's calling an API to open the file for write access for some reason just after copying the file(s). I remember someone here reporting that Norton anti-virus for some reason tried to open Reflect backups for write access during its full system scans, which caused it to set off Image Guardian. Also note that if your backup replication mechanism involves syncing purges/deletions from your NAS to your target, i.e. using your Xplorer2 application to delete files on your USB drive that no longer exist on the NAS, Image Guardian WILL prevent that. If that's a problem for your strategy, then you may need to disable Image Guardian on this USB drive you're using. You can do that without disabling Image Guardian system-wide, and Image Guardian will remember that it should be disabled on that disk even if you disconnect it and reattach it later.