I've just started a new playthrough and with just a few hours in, am experiencing quite a few NPCs getting stuck. I got it quite badly with Camilla (I know she gets stuck quite often though), and then with several NPCs in Solitude and Riften. And even the necromancer outside Boulderfall Cave.
I have several mods active, but I'm pretty sure my last playthrough (which had the same mods) rarely had this issue.
Does anyone know why this happens? Should I restart with a new game?