It’s probably NOT the issue, but I do a bunch of QT development and often have translation PRs from outside. Sometimes, those will not cause a build to fail, but the translations may not be produced if a single translation has errors. Often I’ll see that all translations UP to a specific language have been produced but none thereafter (alphabetical order). Just today, I had NO translations produced. The build was fine, app runs, but only in english. One culprit translation caused that part of the build to fail.
Just an idea.
EDIT: I test from the cli with LANG=nb application-name for quick turnaround.