I feel for you. That's the worst that can happen on stage. iOS does not have a console. Debugging these issues is only possible if you run a debugging session in Xcode while a computer is connected. Although that's not possible if you need to debug usb audio interface problems as you can't connect a computer and the audio device at the same time.
I guess you only have two options. If you want to stick with ST2, you will have to downgrade iOS to version 12 as long as that is possible. Or you need to switch to ST3.
I don't have an iconnect interface but I am currently playing around with a M-Audio M-Track Hub and that seems to work fine so far (and can also be used to connect usb sticks as it is a powered hub 😉).