Auto-negotiation problems are common; they result from errors on the Ethernet devices connected to the appliance, causing dropped packets, reduced throughput, and session drops. Devices that are connected, such as the router or a LAN switch could also switch from full-duplex to half-duplex (and vice versa) because of auto-negotiation problems, resulting in poor network performance.
In some cases, if a duplex mismatch occurs when the interface is auto-negotiated and the connection is set to half-duplex, or the auto-negotiation does not provide the optimal outcome. As a result, manually setting the duplex setting might be the workaround to avoid this problem.
Many users prefer to manually set the speed and duplex mode of the Ethernet NICs so that it will not re-negotiate. It is acceptable to manually configure the duplex settings provided that the peering devices do not always change. Keep in mind, documentation of the settings is also important: some users do not remember changing the settings and report a faulty interface after encountering a problem connecting with other devices.
As a suggestion, set the duplex settings to its optimal state, 100/Full Duplex or 1000/Full Duplex (in the case of Gigabit) on both connecting interfaces (or both HDX depending on the requirement), and monitor the collisions.
You can adjust the interface settings on the ProxySG in the Configuration > Network > Adapters tab.
For information about collision in a network, please read the following FAQ:
What could cause the ProxySG to generate collisions on the network?