After spending  minutes trying to set up the CARM handoff, I found that the cable from the COMM PLL to the Common Mode Sigg-Servo-Board was left disconnected. Then I spent another  minutes to figure out that this signal is actually broken: it is stuck at +10V. I left it disconnected from the Common Mode Sigg-Servo-Board, but connected to the scope as proof.

Should be fixed tomorrow.