aaah....maybe I know.
You have the OLD mixed board V2, then two Midi OUT connectors are reversed!
On new mixer board we have inverted the connectors, but I dont remember why..long time is passed.
try to select on live arranger the EXTout1 and use then the Midi OUT 2
Or Extout2 and use the midi OUT 1
try it, I think must working there too.