@8411guy let me know your finding please

  @KPejman neither the media converter or the Sfp+ changed the issue. Must be something in the firmware?

  @8411guy most probably. I'm trying to call the support and see if they know anything about it. 

  @8411guy I tested with the media convertor as well and no difference for me either. :(

on a call now with support and see if they have any suggestions. 

  @8411guy the MikroTik S+RJ10 didn't do anything for me either. 

I talk to support and they collected some screenshots and they said they get back to me. 

  @8411guy I experienced something interesting. 

• I installed my firewall (Firewalla Gold Plus) between my er8411 and my switch (TL-SG3428X) using the SFP+ modules. my download speed went to 100Mbps only.
• then I replaced the SFP+ module that connects my Firewall to ER8411 to Mikrotik and my speed went back to 750Mbps down and 50Mbps up. 
• then I replaced the SFP+ modle on my switch to Microtik but the result was the same. 
• I then SSH to my firewall and did the speedtest directly on the firewall and I get 1.8Gbps down and 50Mbps up ( exactly what my ISP service is).
• but when I check from the PC or any other device connected to the switch the speed is not what I expect. 

I'm wondering if there is a conflict or somehow some setting mismatch that is part of the firmware between the ER8411 and Switch ? 

I ordered a 2.5G NIC card to see if I connect my PC directly to ER8411. that makes any difference. 

I'll share more finidings. 

  @8411guy today I switched my WAN port from SFP+ port to one of the !Gbs ethernet port and set that port as a WAN.

• right after that I get 980Mbps download from the same ISP and same modem.
• if I connect back the modem to SFP+ Wan1 port then the download is reduced to 500Mbps. 

I have a 1.Gbps download speed from my ISP so connecting directly to modem gives me 1.7Bbps download. 

it's really confusing as why when I connect the modem to SFP+ port, I experienced reduced download speed!

  @8411guy I did more testing, 
 

• I run my man mini with direct cat6a cable to my XB8 modem
  • download 1.7Gbps
  • Upload 52Mbps
• connect the same cable now to my TL-SG3428X switch (ER8411 is still my gateway connected to XB8 modem)
  • download gets to 740Mbps 
  • Upload remains the same 
• I removed my ER8411 and put my old ER7206 back and my Man mini connected to my TL-SG3428X switch
  • download 980Mbps (since the port is 1Gbps on the ER7206 this is very good)
  • upload is the same
• then I connected back my ER8411 back and connected it to my TL-SG3428X switch
  • turned on Flow Control on the uplink port of TL-SG3428X which is a 10G SFP+ port
    • Download went to 230Mbps
    • Upload 10Mbps 
• then connected my Mac Mini directly to ER8411
  • download 230Mbps
  • Upload 10-20 Mbps

conclusion: I think the ER8411 has the Flow Control on by default and somehow it forces the port to transmit at lower speed. I think this is a software bug that can be fixed. 

there is no option on the omada to change the port settings for ER8411!!!

  @KPejman I can see flow control but have no way to disable it

  @8411guy where do you see the flow control setting on ER8411 ?

I can't find it.