Trados Studio - "The detected target language does not match that expected by the project" error when trying to translate XLIFF files with English target language

When creating a project (either with the default, or a custom project template) from an .xlf/.xliff file in which the target language is coded as "en" or "en-uk", the project is created without any errors or warnings, but the created .sdlxliff cannot be opened, with the error message:

The detected target language does not match that expected by the project

This situation was reported to Development and a fix will be provided in a future release of Trados Studio. 

To resolve this, you can:

1. Translate the files individually, as single-document translation

2. Create the project with the target language English (United States) instead of English (United Kingdom). (Create a new TM or add your memory as AnyTM.)

Language code mismatch - situation was reported as a defect.