Terrible Glitch Affecting My Artwork

Hello, this is a question, with a hard to find answer.

First off: Macbook Pro, Processor 2.5 GHz, Memory 8GB,   258.96GB free of 499.05GB

               Ad Ph CS6 version 13.0.6

Im an Artist who often draws pen and ink, and colors digitally. A page from comic will look like this

Very nice. Until a week or so will pass. Ill open up the file, and this will meet me....

I dont know, and cant remember, any significant action of mine to affect my files like this. The top layer of linework vanishes, even tho the layer remains. (Its just empty now) and squares of colors will disappear. If you try to fill them in with color a glitch distortion will appear.

Please help, This has been happening for some time, and many of my pages have to be recolored after many hours of work. Thank you for any information you can give.