Using

• WordPress Multisite (subdir)
• Child themes
• Loco Translate

The Issue

One of our multisite sites isn't string translating (Japanese). We started with non-multisite with just English. Then, converted to multisite and introduced German. The idea was each multisite would serve as a locale. Each multisite site would receive its own theme inheritance from the original theme. String translation seemed to work correctly after some debugging and fine tuning. Later, we added French and Korean and that was a breeze. Now, Japanese isn't working for us. The other languages do, though.

We utilize Loco Translate to handle the translating locally, then commit the generated .po and .mo files in Git before deployment. The translations have already been put into the Japanese side and things just aren't working to replace template strings like the other languages handled it. I've set locale in the dashboard as well; doesn't help.

I've checked everything I can think of, and looped in other developers to no avail. The textdomain matches and the locale is set. The language files for reading in are being correctly created and put in the right places. I'm actually starting to wonder if this is an mbstring thing of some sort; like maybe the regular translation functions in Core aren't handling multibyte characters or something. But I have to imagine they've already thought of that in the __() function, right? That's why we use the textdomain and the files; which need to match up in order to get a text swap. Only, that text swap behavior isn't happening for Japanese. We can put Japanese text into the WYSIWYG textareas content-wise, but it's the theme strings I'm trying to get handled here.

Really running out of ideas on this one. Hoping someone might have some idea of what's going on.