I’ve been tracking this problem since I have a similar situation, although my desired local language is Spanish.
When I made the update to OJS 3.0.2, I notice that some of the labels were missing, and I thougt that part of the translation was incomplete, but then I notice that some labels weren’t there even when the file was ok.
I made a lot of tests, and now I think the problem is related with the language you set as locale when making the update:
When I made the update, I set wrong the locale to English, and I have problems when I change the language to Spanish
Then I made a copy of the backup of the old instalation to a local instalation and made an update, setting the locale to Spanish, now it works ok with Spanish, but I have problems when changing to English
I also notice that some of the data on the database were wrong in my local instalation, where the data is complete just for Spanish.
I can complete the data in that table and solve the problem, but I hope this helps to detect the problem in future releases.