Just clicking on an avatar in the scene causes the scene to be marked as modified. In most cases this is just annoying as it prevents you from telling if the scene is saved or not. However it causes a big issue if you are like me and use prefabs to save variants; because the prefab attempts to auto save changes and thus will get stuck in an infinite flickery loop. I have found that collapsing the descriptor allows it behave normally. Perhaps caused by one of the gizmos or something? This didn't used to always happen, but has seemingly become increasingly common with each update.