I wonder if, depending on the meteo, the lightenings seen by the Mansi could have been sprites or halo
They're forming over large clouds, and it seems the weather was quite bad the morning before. The big clouds would have been a bit further away, with a clear sky above Dyatlov pass : favorable condition for a sight I think.
It seem there was 2 people outside ("on duty" ? for a pee ? Whatever.) They would have call everybody out ( not being afraid, but just amazed.), with no shoes and no gear. They planned to stay close to the tent, but something else then happen.
Those lights could have been mistaken by KGB for aliens ; thus explaining the disparition of 9 picture from Zolotaryov's camera, and maybe even the fact he was having a different camera. (It may just have been the best for night picture ?)
It does not explain more than just the light sights (maybe some pictures ?), but that's a point nobody seems to look at ! :)