Interface\FrameXML\MailFrame.lua:623: bad argument #1 to strupper (string expected, got nil)
This is the full name of error, it only started after latest server maintance. I'm not only one I see people talk about it in my guild aswel. I contacted ingame support but nothing helped I did everything as instructed by GM team but nothing worked so he told me to post it here. This error pops up when I try to send ingame email to one of my alts it's only tied to One character while others function just fine. Also same character that getts lua errors he got bugged friend list, which keeps disappearing and appearing thrown all over the place where it doesn't show people who are online and then offlined. Instead it's messed up totaly.
1. I reinstaled game- clean instal.
2. Tried to delete, WDB, WTF, Interface folders (yes after I deleted these I got ingame cinematic upon launching wow, including all of my keybinds and video settings has been resetted).
None of these worked, I see people complain about it even tho they do not have any addons instaled so this issue is not addon connected at all. I think it is server sided hence it only affects some characters while others work fine.
So any answer or help is great thank you.