An archive bit is an indication of what needs to be backed up.
If another backup system is changing the archive bits there can be havoc. We do not clear the archive bit. Instead, we compare the modification date to our last referenced date.
If another backup system (such as Symantec) is archiving data and creates an archive bit it can cause issues with the CFA.
When a file set’s Preserve Access Times is enabled, then archive bits will be cleared on files backed up. When changing a file set you may wish to enable No Full On Change to avoid running a full backup, which normally happens whenever a file set changes.
File Sets › Starting Directories and Files › Edit (choose one) › Preserve Access Times.