node2 does not seem to work, no DHCP IP address

I finally received 2 CM4 modules after a long time and used them to start up my Turing Pi2 board for the first time today and promptly have the following problem:

Node2 does not seem to work, it does not get a DHCP IP address. The CM4 module #1 works in all other slots without problems.
If I take the CM4 module #2 for comparison, I get the same error: Slot 1,3,4 no problem, the CM4 gets a DHCP address. Only slot2 does not work, with both CM4 modules.

Unfortunately slot2 does not use HDMI video output to check if it is only a network issue or if slot2 refuses to work at all.

Any hints?