We have one website with a main language and two sub languages.
The site is running DW 9.5.0 with Rapido 2.1. This is how it can be reproduced.
1. Create a new page in the main language.
2. Create a new element on the page with item type "Paragraph container".
3. Add a new "Paragraph" to the paragraph container, and type the text "Main language test".
4. Switch to a sub language version of the page, and activate the paragraph container.
5. Edit the paragraph in the paragraph container and change text to "Sub language test".
6. Verify that both language versions display different texts.
7. Switch to main language, and change the text in the paragraph to "Main language test update".
8. See that it has changed on all language versions, and overwritten the change made on the sub languages.
If you do the same operation on a simple "Paragraph" element the sub language version is NOT overwritten.
It does look like it only applies to the "Paragraph container" element.