I can only speak from observed experience with no data but I suspect infection from the eye damage. One of my favorite octopuses (Octane) climbed out of his tank and was not discovered immediately. He was still alive but the overhead fan had dried some of his skin. Over the next few days, he chewed off sections of multiple arms and then died. I am not sure (and I don't believe we have direct bacterial evidence) if Autophagy is a specific bacterial infection or can be the result of any infection that irritates the skin so contagion is confusing. In Octane's case, there was never a problem for other octos in the same tank.