Cannot delete feature branch because of a lock file on the server

No user can remove branch , because of lock file on gitlab server.

remote: error: cannot lock ref 'refs/heads/feature/WM2-1040': Unable to create '/var/opt/gitlab/git-data-file03/repositories/wiremo/wiremo-dashboard.git/./refs/heads/feature/WM2-1040.lock': File exists.
remote: Another git process seems to be running in this repository, e.g.
remote: an editor opened by 'git commit'. Please make sure all processes
remote: are terminated then try again. If it still fails, a git process
remote: may have crashed in this repository earlier:
remote: remove the file manually to continue.
 ! [remote rejected] feature/WM2-1040 (failed to update ref)
error: failed to push some refs to ''