Came back to LE after a few months. Now I’m finding often (always?) nemesis are invisible when I summon them. This last for several seconds only, but they have time to cast a few attacks in that time. Those attacks can do huge damage to me and I cant see them doing it.
At first I thought it was just letting the game load, but if thats the problem, game tries to load them all the time.
This was not the case before. Just pointing out this annoying thing. 
Edit: Its not just nemesis it seems. During the campaign as I leveled a character, i found mobs not appearing. There was even a questline that didnt trigger. Those things in the sewers in the imperial era quest. Those three mobs did spawn, but they were invisible. They did not appear on map or even were possible to damage(?). Only way to fix when non nemesis mob is invisible is to portal out and come back. At least thats the only thing that works.
I hope this doesnt happen in monoliths where I would need to reset and start over when something should kill just isnt visible.