The power button trick no longer works. Indeed, it now has the reverse effect of removing the keyboard focus and even disabling Ctrl+Backspace (which is still there usually when keyboard focus is lost after coming back from the task manager)! However, in such situations, I can still tap on the LXDE menu with the stylus and shut down LXDE regularly. I remember having once also lost the touchscreen, even with the power button menu frozen, where I had to do a hard shutdown. But that was prior to PR1.1.1 I think. So avoid the power button when in LXDE!

EDIT: Just discovered a way to get to the Task Manager when everything else fails: Open the camera lens and close the camera app again!