Remote: error: cannot lock ref

Hello, i’ve got a blocker that is impacting in my companies work.
i’m getting the bellow error wile making a git push As shown in the images attached:
remote:error: cannot lock ref ‘xxxxx’ : reference already exists.
!remore reject xxxxxx (failed to update ref)
This keeps appening for 2/3 minutes and after that a new push works very well. Also during this time the gitlab projects page gives an error 503. Can you help?
The gitlab version is - GitLab Enterprise Edition 11.1.4-ee