I have the same Deja Vu server with the same JCAT NET CARD XE.
I own both the eno and the muon (non PRO model) and both of those filters work fine with my server, coming out of a Silent Angel Bonn N8 Ethernet Switch. However, my internet service is only 200 mbs. Is your 1Gb/s Ethernet cable coming out of a switch that does not accommodate 100 mbs? I did have the same issue as you when I was running fiber through 1,000 mbs convertors and per Rich Truss at Network Acoustics, I had to purchase convertors that maxed out at 100 mbs. I did that and it then worked fine. I now run Ethernet directly from my router into the Bonn N8 switch and then into the muon. Based on the amber color of the light on the switch, it is only operating at 100 mbs into the muon, but it works and sounds just fine. I wish they would just stop coming out with new stuff for us to purchase.