image darkens and then go back to the regular tone from continuously

After updates on Beta & regular Photoshop, when I am editing an image it will shift to a darker tone for a while & go back to original tone. It does this continually. How do I make it STOP!? It even does this when working with layers! I set image profile (the gray gamma) & made sure images is converted to same profile, however my images continue to go dark & back to original version.