VxRail E460F vs ESXi Windows VM Slow NIC Performance

Running a cluster of three VxRail E460 hosts w/ESXi 6.5. Recently changed the Windows VM NICs to VMXNET3 in order to get 10G speeds. Although Windows is reporting 10G connectivity, a file copy job between VMs has throughput at 0.13% of the speed.

VMs were on seperate hosts. Tried moving them on to same host with worse performance.

This is a new problem for me. Probable a question for VMware. But looking to see if anyone else has experienced this?