How are you still using that module?
I have used it in the past, but it has not been updated for a couple of years now.
I warn you, solving this problem will lead to some other problem! You are better off finding a new multi-lang solution (like
this one made by Rolf)
The problem you are now experiencing was 'caused' by some changes in the CMSMS core somewhere during the 1.9 to 1.10 or 1.10 to 1.11 upgrade. More modules were effected by this little change.
The solution to your question is actually quite simple and is explained in
this topic
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Not sure, but from memory I believe that right after you solve this trivial problem, babel throws a new one at you. I might be able to find reference to the way I solved that error back then.
But really, I must warn you: babel is not supported anymore and more things have been broken during upgrades of the core of CMSMS.