This .. *might* be my issue as well? Lots of characters have lost their default tokens (including a bunch of spell templates). I did convert one page, but I didn't have all those spell templates on the page. Pretty bonkers. Double-checking, there's still "a token" but no picture, won't drag, and like mentioned above, all the attempts to drag show up as soon as a real image/token is attached. I've fixed all the ones I've found by dragging the Portrait, editing, deleting the blank token, then resizing and assigning the portrait image as the token again.