Nostalrius Begins - Quality wow vanilla realm (1.12)

I keep getting wow errors when I use my mount and when I use hearthstone on any of my characters. Any idea why this happens? I don't really want to delete wtf folder and reset all my ekybinds and addons. Or is there a way to do it and copy the files to keep my addon and keybind setting?

Any ideas would be great as hearthstone goes on cool down but doesn't take my toon to the target location.