Where did the tokens come from? From your art library? From the monster manual or a module? I think I have seen other people complaining about token issues when the tokens come from their library. I can say I've never had this problem, but I have never used a token from my library, they either were attached to the creature to begin with or I make them and upload to the VTT and then attach them to the sheet. To be clear, when you double click the token does it say represents whatever npc it is supposed to? And, has it been saved as the default token by opening the edit function on the sheet and saving it as the default token, not the portrait for the npc? Do your PC tokens have sight enabled, are they set as representing the corresponding character and have they been saved to the corresponding character sheet as the default token? Other than these things, I have no idea what could be causing your issues, in which case, hopefully someone will officially answer the post.