Jorge,
it is because there should not be passthrough for mark-connecction rule.
I did not understand what you mean...
If I am marking different connections then marking packets packets or routing, I need to set passthrough = yes or am I wrong?
Example:
add action=mark-connection chain=prerouting comment="" disabled=no dst-address=10.0.0.2 dst-port=123 new-connection-mark=abcC passthrough=yes protocol=tcp
add action=mark-connection chain=prerouting comment="" disabled=no dst-address=10.0.0.2 dst-port=123 new-connection-mark=abcC passthrough=yes protocol=udp
add action=mark-routing chain=prerouting comment="" connection-mark=abcC disabled=no new-routing-mark=abcR passthrough=yes
Best
Jorge