As the titles says, had the "Unsubscribe Feedback Page" for two different clients presenting the feedback options to unsubscribers in French, German, etc., not in English like it should.

And no, it wasn't due to user preferences, embedded web translators, etc. 

SOLUTION - Go to ZMA  > Settings  > General Settings > Unsubscribe > Unsubscribe feedback page

Edit and fiddle with it, re-save, inexplicable other language presentation should go away. All of above verified by unsubscribing with test account.