There is a policy configured for suspected virus to strip and delay attachments in Suspect Virus Quarantine. Also there is another policy for content filtering module to remove attachments found. As result of first policy message is split into 2 copies, one going into Suspect Virus Quarantine, the other one getting delivered to recipient with attachment stripped. However when the copy of the mail in Suspect Virus Quarantine gets released strip action resulting from content filtering policy doesn't get applied. Message Audit Log shows strip action as applied twice.
This issue has been resolved in version 10.5.3. Please consider upgrading to this version to resolve this issue.