RAX120 and XS708Ev2 not connecting at 5Gbps

Hi

I have a RAX120 connected to a XS708Ev2 (10Gbe switch) and both ends only show 1000Mbit connection.

Both firmwares up to date (RAX120 on 118 beta).

Other devices (RN524X and RN516 with a 10Gbe board in) both connect and show as 10Gbit on the XS708Ev2.

Any advice??
Thanks

Andy