Audio Synthesis Dax Decade lock issue with ADX module

Hello,

Once again with a DAX problem. I now have a DAX decade balanced that works great on all inputs but it came with the ADX analog to digital converter that allows to use 3 different analog inputs with the DAX and its built in preamp. The DAX sold with this option have an additional board and a differently programmed Microprocessor. My issue is that the DAX can command the ADX module, correctly switching between the 3 inputs but it doesn't lock on the digital signal fed back from the ADX through BNC coax. Any other dac I tried, equipped with a BNC input does lock on the ADX without a problem and it sounds good. The actual BNC input on the DAX works fine with other sources.

At one point the DAX managed to lock on one of the 3 inputs but displayed Ncode on the screen and there was no sound.
 
Unfortunately I did not manage to get schematics for this model.

What's strange is that the transmission seems ok because any other dac locks on the signal just fine and the reception seems ok as well because the dax itself locks on other sources with the bnc connexion.