Blizzard UI Errors MOP

Hello There

I just recently downloaded the MOP-Expansion again and decided to play it after a while, hoping PvE got implemented (Spoiler it did but nobody seems to care for it =(
Upon trying to join a BG i encountered the first problem, i couldnt join. Whenver i pressed the join button the message "Blizzard_PVPUI has been blocked from an action only available to the Blizzard UI. You can disable this addon and reload the UI." Well guess what, i dont have any addons (besides the Raid Profiles which doesnt show up in the MOP folder.
Now since PVP isnt something i do a whole lot i could have lived with this. But the same message (different section e.g. glyphs / time / guild) pops up whenever.
I have written an ingame ticket which quickly responded in an answer i already did, delete cache, delete addons. Since this didnt work i hope someone in the forum might have encountered a similar problem or is smarter than me and able to fix this =)

My thanks

follow these steps:
1) open your MoP folder and rename "interface" and "WTF" into "interfacebackup" and "WTFbackup"
2) go here: https://www.warmane.com/download choose "Mist of pandaria", when the torrent shows which files to download you have to select ONLY "Interface" and "WTF" folder
4) place them inside your MoP folder
5) Start the game

A guy who has your same problem solved by doing that