The issue from my original post "DP83867IS: SGMII Problem with different chip revisions" is still open. In the meantime, I managed to get access to all PHY registers.
Regarding @Nikhil Menon's question from Feb 23: I accessed register 0x0001 on all devices and all 5 devices respond with 0111 1001 0110 1101, which implies that the auto-negotiation process is completed and that a valid link has been established.
Still, only one of the devices is reachable via UDP (all running the same bitstream). Which registers should I investigate now?
Thanks and best,
Nico