I suspect that this is actually a bug in iPadOS. I've had issues with the USB-C to 3.5mm dongle, including a period of time in which it was completely non-func

I suspect that this is actually a bug in iPadOS. I've had issues with the USB-C to 3.5mm dongle, including a period of time in which it was completely non-functional. But then a week ago I noticed out of the corner of my eye that my iPad (the new Pro 11) was rebooting itself. And now the dongle works perfectly again. Give it a shot - if it starts acting goofy again, reboot your iPad and see if that "fixes" it. I'm going to pay attention to it for a while and file a bug report if it looks to be correlated.