Hi! i have the same situation when i tried complete the mission "The Legacy of the Hangmoon" i cant complete it because that error.
The error: Message-> Package files are corrupted. Use Check Files to restore them. (C:\Program files(x86)\NCSOFT\BnS\bin64\..\contents\Local\ncwest\english\CookedPC\00028826.upk)
I have already do"Check Files" but the same error continues.