Windows (install.wim) and WinPE (boot.wim) each have separate Language update files, they are not interchangeable. You cannot apply Windows LP's to boot.wim, and WinPE OC's to install.wim.
If you're using the NTLite feature to apply the same changes to multiple image files (in the same processing run), you can't leave it checked for boot.wim when LP's are present in the Updates list. You would have to perform two separate passes.
There is no Basque OC for WinPE any way.