Coloring game problem with ipad

I have been paying for and using the Colorfly coloring game and my iPad is pretty new. Every time I get the colors almost where i want them in the game the picture and the game close on me and when I open my picture back up it returns to a previous time where I didn’t have all the vibrant colors the way I wanted them this happens repeatedly and is very frustrating I can’t finish my picture. What could cause this? I can’t seem to get an answer from the company I am paying for the game to work properly I would appreciate any help.