If you go to the Globalization Manager, select a business object. Then select a secondary language, change the label of a field, and Save. If you are using Firefox, it does not save or give an error. So you do not know that it did not save, until you go back into that BO and look at the field.
As a temporary fix, use Internet Explorer 11 and it will save just fine. Moving forward, secondary language values in the Globalization Manager can now be correctly saved in the Firefox browser.