You have observed entries in debug logs like the following, and you are concerned that Antivirus is checking each file multiple times:
The above entries in the logs are the expected behavior of the Kerio Connect Antivirus. The antivirus creates a temp file every time while scanning an attachment or email to test it in the isolation. After the scanning is completed, the temp file is deleted. The same process repeats every time at the same location giving an impression of AV is scanning the same file multiple times.
Agents only: For further information, refer to this article: Reading the Antivirus Debug Logs