Okay, I understand.
I suspect there might be something wrong with the translation file. It is generated via Poedit, and I suspect something might be missing there. I did a few tests, and re-generated the original POT file with wp-cli instead. I will try to automate this process for each build.
Can you try this attached POT file instead of the original one? It should resolve the problem, as it is generated specifically via wp-cli.