I don't know about other apps, but for Ibis Paint users,

To prevent the unfortunate incident of your drawing file getting corrupted, please make sure to properly close the app when you stop drawing. Even if the file gets corrupted, you can auto-recover it with the press of a button, but it rewinds all the strokes of the drawing, so it takes a lot of time for complex drawings. I didn't want to know this either. (The picture is a drawing I made to use as a Minecraft server icon.)