Cisco Switching/Routing :: GLC-T In C3KX-NM-10G - Full Duplex Does Not Work

I have C3750X with C3KX-NM-10G, and have-T SFP in slot 3 ( means it is not in SFP+ slot ).I need to set speed&duplex hard to 100/Full, but if I do the link goes down. I have the same settings on the other side, only IOS version is different.I tried other speeds - 10 and 1000, but no one works with Full. When I change duplex to Auto it works fine.The reason why I am doing this on C3KX-NM-10G is because I need to use NetFlow and cannot use the chassis' copper port. At the moment the ports are connected through a copper patch cord, but in full production there will be a radio link in between that requires 100M/Full to be set hard.I am trying to search for any document that would describe this limitation, but cannot find any. Also port capabilities do not indicate duplex could not be set to full:

show interfaces g1/1/3 capabilities
GigabitEthernet1/1/3
  Model:                 WS-C3750X-48P
  Type:                  10/100/1000BaseTX SFP
  Speed:                 10,100,1000,10000,auto
  Duplex:                half,full,auto
  Trunk encap. type:     802.1Q,ISL

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