1 Gb AIR/RoonReady - when I got it working!

[daniel.avasilichioaei]

I'm not sure that I understand correctly your setup, but I suppose it is working because of the route: Internet->Router->PC->WLAN-Repeater->D220 Pro.
PC->WLAN-Repeater seems to communicate via PLC (limited to 140 Mbps) or via WLAN (limited to 526 Mbps). So, WLAN-Repeater will never send to Devilaet 1 Gbps (witch MS->Switch->Devialet is doing).

via WLAN. Yes it will never send 1Gbps, but that is not the problem with the 1Gb connection to the Devialet, even DSD64 needs <10Gbps.

Please check this post https://devialetchat.com/Thread-Roon-RAA...8#pid85978 (#278), and also the next one (#279).
WLAN speed limitation may act similar to USB 2 speed limitation from my post. Even your “technical” connection speed is 1000 Mbps, the “actual” connection speed (data traffic) is limited to less than 1000 Mbps by WLAN. As per thumb5 post #279, "Furthermore that limit on the bandwidth seems to avoid hitting the error condition".
Still, I cannot be sure this is happening in your situation also...