I think the cause of some of the flaky behavior is the difference between how a Windows or a Mac computer treats applications and how Android treats them.
Android doesn't entirely kill apps when you exit from them, it leaves them in memory in case you want to return to them. This is a good thing because when you go back to an app it doesn't just start at the beginning again. Instead, you can mostly go back to where you left off.
However, all software has bugs, and when something goes wrong due to one such insect, that error too will stay in memory with the app. The only way to really force the app to reinitialize (at-least with the tools in a nonrooted NC) is to fully shut it down. That isn't the only possibility. There are also cases where the bugs are in the Android kernel and drivers, and, of course, nothing shuts that down except a full power-off.
The moral of the story is that if something is behaving strangely, it is not enough, usually, to just "exit" the app, and "restart" it. You probably should try a full power-off before you panic too much.
