I can't repeat this one as it was a freak accident, but it resulted in me having to force quit the app.
I was working on my latest track in the sub synth, I fumbled my phone, caught it, and when I looked at the screen, it was in the waveform editor. No big problem you might think, except neither the back arrow at top right, or on the device would exit the editor! Every time I pressed the back arrow I got a brief flash if the subsynth then it went straight back into the waveform editor. The only way to get out of it was to force quit.
Happy New Year by the way!