The HNAS side has a flag showing if a file is clean or not. If the file is not set to clean, the HNAS system submits several scan requests to SPNAF to scan this file.
The issue happens because the Virus Scan Action is set to "Bypass" so when an infected file is detected, no action is taken on this file. Thus, the flag will not be set to clean and HNAS keeps sending scan requests.
To resolve the issue, do NOT set the Virus Scan Action to "Bypass". You should configure the first action to "Clean" and the second action to "Quarantine".