In short, playback anything in Auria (via the interface, of course) and, while it's playing, go to Menu->Settings. For me, that makes the UR44 go into a sort of infinite loop/echo which can only be stopped by quitting and restarting Auria and/or power cycling the UR44. It is totally repeatable, even after rebooting everything.
Patient: "Doctor, every time I stand on one leg and turn my head to the side, I feel pain in my right thumb."
Doctor: "Well, don't do it then!"
Yes, well I would not normally go to Settings during playback (I did it by accident, when aiming for Menu->OutputMatrix). Nonetheless, it would be good to determine what Auria is doing that upsets the UR44 so that either Steinberg/Yamaha can be informed of an issue on their side, or perhaps @Rim can perform some of his magic to avoid triggering the issue in the UR44.
It might be helpful if a handful of users of other popular interfaces could try the above test and report their findings too. Maybe it's not specific to the UR44

Many thanks

iPad3/64 - iOS v7.1.2 / Auria v1.154 / Steinberg UR44 v2.1.1