I understand the issue you're having. Given that the texts are part of the Shoptimizer theme, please follow the steps below and make sure that everything is translated properly.
- Please go to WPML > Theme and Plugin localization
- Select the Theme and scan for the string
- once the scan is completed, search for the strings in "WPML > String Translation"
- If that appears untranslated, add the translation by clicking on the "+" icon.
As the translated content is visible when the page initially loads but vanishes after switching languages, it could also be associated with caching. Please clear the caches from the site, browser, and server(if enabled) and check again.
Please let me know the update. I will be happy to help if you need further assistance in this matter.
The cache is cleared several times in the WP back-end, server, and Cloudflare. I use Autoptimize, WP Fastest Cache and Asset Cleanup advised by the Shoptimizer developers.