@Network-charles: I think what happened is that your changes would have had to be marked for translation. It would probably make more sense to use Extension:LabeledSectionTransclusion (but you have to use manual section tags rather than the lsth parser function because of more translation issues) rather than onlyinclude tags though.
They would also have to be marked for translation, but the failure mode would be no output at all, not transcluding the entire page.