Hi,
yesterday I noted per chance that the virtually missing rods are at identical positions at both units. So I started to count: Actually, no rod is missing at all! All 25 rods are present in any unit. I've just been misled. The two holes were deliberately left empty at factory, probably to mechanically match the pedal key assembly. I also managed to pry open the contact assemblies and found that under one of these open holes there's no contact pair at all.
Issue solved, question answered, thank you.
Best regards!
Uwe Menrath