Samsung s-pen users: does this app lock up as soon as you start to draw with the s-pen? Try tapping the pen once on the start-up pic (the one with all the tools) as the app loads. Also, avoid saving or drying any wet layers made with any of the first 3 watercolor brushes until you switch away to a different tool first. But the 4th WC brush will dry/save okay. Otherwise the app will lock into a save (or dry) loop and/or corrupt the file.