D8: Why updated paragraph content does not lead to an updated translation?
To expand on the comment from @4k4, for most use cases, you want to make the paragraph field untranslatable because it just stores the references to the paragraphs, which are then being translated.

Then you always have the same paragraphs in the same order for all translations.

Translatable paragraph fields are not yet properly supported (this is being worked on in the issue queue) and it should only be done if the paragraph structure must be different for different languages.