We do not have all details. But I asume that he has H9 Max and H9 Core. In that case most userrs would max Core, so in reality he most probably has two identical units in Max configuration.
So, most probable is kind of hardware (or firmware or setup) problém on his H9 Max.
Or there might be also problém on the units in MIDI chain before H9. MIDI splitter sould bring the solution.
