iperf multiple simultaneous port testing, with server with 4x1gb LACP ports.

I have a server with 4x1GB LACP ports bonded. The switch ports are set correctly.

When I test multiple simultaneous iperf tests to this server, some of the results allow the full lane of 1GB simultaneously, but some workstations do not.

For the case of this example if I have 2 workstations testing, I expect full 1GB each. What would cause it to drop the transfer 50% on some workstations but not others even though the workstations I am testing are on the same switch.

Thank you for any suggestions.