Overriding translations in a custom theme only works for English. Once I switch to another language, the original text is shown instead of the custom translation from my theme.

To reproduce:

• Set 'theme.use' => 'themetim:tim',
• Set 'language.available' => ['de', 'en', 'nl', 'fr', 'es'],
• Set 'language.default' => 'en',
• Deploy attached theme inside modules-directory.

themetim.tar.gz

• Go to admin-login and switch languages to see that only the English language show the custom translation.