Multiple devices are displaying the same wrong MAC address in audit

There is a feature of Layer 3 switches called Proxy ARP. When enabled, Proxy ARP causes the switch to report its own MAC address for devices behind the switch. As a result, every device behind the switch will appear to have the same MAC address.

Proxy ARP was originally designed to deal with misconfigured subnets, but today it is used for network address translation. For more information, refer to Proxy ARP.

Datto RMM is correctly reporting the information given to it when Proxy ARP is used. Modern switches should have a way to disable Proxy ARP if it is not needed.