Hard coded speed/duplex issues

All, I’m having issues with a RB1100AHx2.

When I hard code the speed and duplex to 100 full on a port it’s a dramatic drop (14Mbps) in throughput on the download?

If the port is set to auto negotiation I get the full 200Mbps from the fiber circuit.

The port in question is not the WAN port but a LAN port.

I’ve tried on 2 different PCs directly to the port and also connected with a Cisco switch.

What gives? Does MikroTik only work properly with auto negotiation?

Anything helpful would be very appreciated.

Have you set the fixed speed on the both sides the same?