Interesting thread. I’m able to easily connect all three of my H9’s to H9 Control via Bluetooth on my MacMini, my MacBook Pro, and iPad Pro. I can connect all three via USB B cable on my MacMini and MacBook Pro using an Anker 4 port USB A Hub plugged into the USB A port those Macs. I do have to be sure that the H9’s are not connected to Bluetooth on my MacMini (“they” try to do that with fierce intensity) and when any one of them achieves that lofty peak of communication, problems start. I will say that with all three plugged into the port has been dicey. There are times when it seems rock solid and I can operate like Dr Frankenstein on the monsters, and then there are times when I’ll lose one and end up having to plug it in to another USB port away from the Hub to re-establish communication. Now THAT has been a bitch at times.
Interestingly enough when I have connected all three to Bluetooth w/cables plugged in (frowned upon by Eventide) they have seemed relatively stable. I will generally, for the sake of NOT having to deal with a messed up box if one does drop communication, unplug the USB B cable.
So to really confuse the issue/question as posed by the OP there seems to be a mix and match for me but to really go rock solid I remove cables if I’m chatting via BT and if I’m tethered, Bluetooth is either off and/or they are disconnected.
I’ve yet to try actually try turning off Bluetooth at the pedal itself when attached to cable…an experiment I’ll try at some point but as a newb to the whole H9 preset game and to MIDI control of the board I’m building (RJM PBC/6X & Mini Effect Gizmo X) I’ll just go with my most solid connection (cable in/BT off) while programming.