M4100 26 POE with no gigabit

Here is the information I've added to the support ticket. It includes a bit more info:

The problem I am having is that none of the ports are auto negotiating to 1000mbps. This did use to work.

The things I've tried so far are:
1. Replaced all patch cables with new Cat6 cables.
2. Upgrade firmware to the latest (shown in "device status" as 10.0.2.30)
3. Factory reset using the menu option: Maintenance > Reset > Factory Default
4. Tested a server connected to the switch with ethtool. The output shows the following "Link partner advertised link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full".
5. Connected a gigabit capable PC directly to the switch using the new Cat6 cable. Speed is still showing as 100mbps.
6. Connected the same PC directly to an un-managed Netgear switch. PC and lights on switch show connection at 1000mbps.
7. Replaced the M4100 switch with the un-managed switch. This showed all gigabit capable devices as connecting at the full 1000mbps as expected.
8. I also tried connecting the M4100 and un-managed switch together using the Cat6. Both sides show only 100mps connections.

All tests were done before and after a factory reset.
After the factory reset all ports did not have anything plugged in apart from the PC I was using to configure the switch.