Opener, congratulations, etc., should only be written and checked in LinkedIn, not in Sales Navigator
Feature 'Always Check Sales Navigator Messages'
Opener messages are always sent where your connection request text is. If you don't use one, the opener will always be written in LinkedIn.
Congratulations are always sent where the chat has already started, either in the LinkedIn chat or in the Sales Navigator chat.
If you no longer want openers or congratulations to be written in Sales Navigator, but only in LinkedIn, you can deactivate this here.
To do so, go to 'Settings' ➔ and deactivate 'Always check Sales Navigator messages'.