There were several reports about ContentTranslation inserting unnecessary nbsp (non-breaking space):
- https://www.mediawiki.org/wiki/Topic:T2rq2dr3end57ptu
- https://www.mediawiki.org/wiki/Topic:T1zw59l2t12nzi3i
I don't have any more information about reproduction, but I should at least file it, because it starts to repeat itself.