Hi and thank you for the answer.
As i feared, it’s not reproductible 
. We don’t use P/Rs Sonarqube functionality as it is not compatible with Gitlab for this version of sonarqube.
As you can see in the screenshot above, last analysis date is 3 months ago fot branch xxx-845. Also, this is just an example as i found some branches aged more than 3 months. Most projects we have that i saw seems impacted by this and i checked via the API to confirm analysis date.
Our developement and staging environments seems to work well that is to say analysis of long-term branches implies removal of short-termed.
I’am going to dump our production database to import it in dev then relaunch in debug mode. If we dont find the error root cause, we will write a script passig by the API to remove old short-lived, script that i will publish here.
Regards,