Xavier

Problem:
String translations are not being applied unless "auto-register strings for translation" is Enabled.

I've rescanned, translated some new strings and the French strings only appear if auto-register strings for translation is on.

There are more than 200 strings so I cannot delete and retranslate.

Could I try to export as .po, delete all strings in domain and import .po?

Solution:
I followed you recommendations, and finally this post solved the issue:
https://wpml.org/errata/string-translations-are-not-visible-on-the-site-after-a-string-has-been-translated/

Relevant Documentation:
https://wpml.org/errata/string-translations-are-not-visible-on-the-site-after-a-string-has-been-translated/