Moving + button
A recent iPhone app update (not sure exactly when) resulted in the "+" button moving while I'm entering data. For instance, I'll push "+", enter my information, push "Save," and when the app returns to the home screen, it momentarily has the "+" button slightly left of center and higher than normal. My finger reacts to push the button where it's located, which results in clicking the wrong thing as the button moves down and center.
I'm experiencing this bug on an iPhone 6s running iOS 12.1.