How to upgrade GitLab from 8.17.6 to 9.x.x in docker?

Hello, everyone.

I recently restored my GitLab instance, which runs in docker, from a backup in 8.17.4 and then upgraded it to 8.17.6 with no problems. Now I’m trying to upgrade it to v9, but when it pulls and runs the 9.x.x image it fails because of task: non-zero exit (137): dockerexec: unhealthy container

it all seems the upgrade process can’t be triggered.

do i need to do anything before upgrading to this major release?

thanks in advance