I have previously used A side to X1 converting copper to fiber and worked well, but did not have other active outputs on A side.
My system has changed a great deal since then. I have added new server, additional switch (PF Buffalo) and additional DAC, Mola Mola Makua, but I still have Lumin X1. I now have fiber coming from PF Buffalo directly to Lumin X1. The etherREGEN now is in use after the PF Buffalo with B side into Antipodes K50 and K50 Direct Stream RJ45 port to Makua. I have found shielded ethernet cable, Audio Sensibility, does not work on A side of etherREGEN, but does on B side, as well as from K50 or directly to Makua from PF Buffalo. I am inquiring with Audio Sensibility, but do suspect it is the shielding/grounding that may not be compatible with A side etherREGEN. I do not have the issue with other ethernet cables I have--generic 5e, Ghent, nor Sablon.