Thanks for that.
Pleased to report the issue has been identified and fixed, for you.
I'm not totally sure how it happened, and even less sure how it happened on two different XF installs, but a single file (as far as I can tell) was a much older version than it should be (perhaps circa XFMG 1.0.x).
As a precaution I re-uploaded all of the XFMG files for both sites and this seems to have solved the problem.