Unable to delete a branch

I'm trying to delete a specific branch from a web-interface but when I ckick Delete button nothing happens, no errors are showen. I can delete other branches just fine, the only difference I've found by now is that problematic branch has a file /var/opt/gitlab/git-data/repositories/Integration/BBRBusiness.git/refs/heads/BBR-1.04.01 where BBR-1.04.01 is a branch name, there was no such file for the branch I was able to delete although it belonged to the same repo. I dont-t know if it's connected or not. Gitlab version is 11.11.0 Any ideas?