There are similar threads about this.
Scenario 1: Evernote quits when the iPad screen is locked. For example, Evernote is open on an iPad, with a note open and being edited. The iPad automatically locks as per whatever is the general iPad setting. When the iPad is subsequently unlocked, Evernote has quit. When it's relaunched it isn't on the last note that was open. This is really frustrating when you've simply stepped away from the iPad for a moment.
Scenario 2: Evernote quits when swapping apps. For example, Evernote is open but you switch to Safari or another app. If you're out of Evernote for more than 30-60 seconds, it has quit by the time you switch back to it. Again, frustrating because you lose where you were up to with your editing.
It's even worse when you're doing something like annotating a PDF and you lose all of your unsaved annotations simply because you had to change apps for a moment.
In both scenarios productivity drops enormously but frustration goes sky-high.
This seems to be an ongoing issue that dates back a long, long time. Fixing this needs to be addressed.