I rarely notice it in Chaos Dungeons but it happens constantly in Thornespire.
I play with an Xbox controller and I disabled the “b” button mapping that would normally be used to manually disable Mayhem. I verified that I can no longer manually disable it.
I am guessing that for some reason it switches when my health gets really low but I am not aware that this is a documented feature.
I am loosing Mayhem about 4 or 5 times per level and with the 30 second cool down the content is a lot harder this way. What am I missing?