After Postgresql upgrade from version 9.6 to version 13 all new scans are pending

We have to upgrade our Postgresql version to 10+ to mitigate some vulnerabilities.
After Postgresql upgrade from version 9.6 to version 13 all new scans are pending.
We are hosting SonarQube and Postgresql on the same linux server (Ubuntu server 20.04.2 LTS).

SonarQube Developer Edition - version 8.9 (build 43852)
Postgresql version 9.6.19



Steps to reproduce:

Stop SonarQube service

apt update
apt install postgresql-11
pg_dropcluster 11 main --stop
systemctl stop postgresql
pg_upgradecluster -m upgrade 9.6 main
systemctl start postgresql
pg_dropcluster 9.6 main --stop

Start SonarQube service.

Hey there.

Checkout this guide.

https://community.sonarsource.com/t/sonarqube-becomes-slow-after-postgresql-upgrade/37925/2