You are not allowed to force push code to a protected branch

Summary

(Summarize the bug encountered concisely)

This is basically the problem: https://gitlab.com/gitlab-org/gitlab-ce/issues/25301

Steps to reproduce

(How one can reproduce the issue - this is very important)

When we want to push new changes, this error occurs.

Example Project

(If possible, please create an example project here on GitLab.com that exhibits the problematic behaviour, and link to it here in the bug report)

(If you are using an older version of GitLab, this will also determine whether the bug has been fixed in a more recent version)

What is the current bug behavior?

(What actually happens)

After pushing code changes to a reposity, master becomes protected for some reason. Then we need to go to settings repository, protected branches and click unprotect.

What is the expected correct behavior?

(What you should see instead)

Correct behavior - master shouldn't become protected.

Relevant logs and/or screenshots

(Paste any relevant logs - please use code blocks (```) to format console output, logs, and code as it's very hard to read otherwise.)

This started to happen when we upgraded Gitlab server from 11.2.1-ce.0 to 11.2.3-ce.0.

Output of checks

(If you are reporting a bug on GitLab.com, write: This bug happens on GitLab.com)

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:env:info)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production)

System information
System:		
Current User:	git
Using RVM:	no
Ruby Version:	2.4.4p296
Gem Version:	2.7.6
Bundler Version:1.16.2
Rake Version:	12.3.1
Redis Version:	3.2.11
Git Version:	2.18.0
Sidekiq Version:5.1.3
Go Version:	unknown

GitLab information
Version:	11.2.3
Revision:	06cbee3
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql
URL:		http://gitlab.xx.lan
HTTP Clone URL:	http://gitlab.xx.lan/some-group/some-project.git
SSH Clone URL:	git@gitlab.xx.lan:some-group/some-project.git
Using LDAP:	no
Using Omniauth:	no

GitLab Shell
Version:	8.1.1
Repository storage paths:
- default: 	/var/opt/gitlab/git-data/repositories
Hooks:		/opt/gitlab/embedded/service/gitlab-shell/hooks
Git:		/opt/gitlab/embedded/bin/git

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Checking GitLab Shell ...

GitLab Shell version >= 8.1.1 ? ... OK (8.1.1)
Repo base directory exists?
default... yes
Repo storage directories are symlinks?
default... no
Repo paths owned by git:root, or git:git?
default... yes
Repo paths access is drwxrws---?
default... yes
hooks directories in repos are links: ... 
9/2 ... ok
8/4 ... ok
8/5 ... ok
7/6 ... ok
10/7 ... ok
7/8 ... ok
2/9 ... ok
9/10 ... ok
10/12 ... ok
10/13 ... ok
10/15 ... ok
10/16 ... ok
10/17 ... ok
10/19 ... ok
10/21 ... ok
10/22 ... ok
10/23 ... ok
10/24 ... ok
10/25 ... ok
10/26 ... ok
11/28 ... ok
11/29 ... ok
11/30 ... ok
7/31 ... ok
17/32 ... ok
17/33 ... ok
13/34 ... ok
13/35 ... ok
13/36 ... ok
6/37 ... ok
6/38 ... ok
6/39 ... ok
12/40 ... ok
12/41 ... ok
12/42 ... ok
12/43 ... ok
13/44 ... ok
6/45 ... ok
17/46 ... ok
13/47 ... ok
6/48 ... ok
8/49 ... ok
17/50 ... ok
6/51 ... ok
7/52 ... ok
7/53 ... ok
7/54 ... ok
13/55 ... ok
13/56 ... ok
6/57 ... ok
10/58 ... ok
12/59 ... ok
12/60 ... ok
17/61 ... ok
13/62 ... ok
12/63 ... ok
12/64 ... ok
17/65 ... ok
17/66 ... ok
17/67 ... ok
18/68 ... ok
17/70 ... ok
6/74 ... ok
25/75 ... ok
9/76 ... ok
9/77 ... ok
13/79 ... ok
13/80 ... ok
9/81 ... ok
6/82 ... ok
16/83 ... ok
13/84 ... ok
6/85 ... ok
13/86 ... ok
16/87 ... ok
13/88 ... ok
17/89 ... ok
17/90 ... ok
6/91 ... ok
12/92 ... ok
6/93 ... ok
17/94 ... ok
16/95 ... ok
17/96 ... ok
17/97 ... ok
6/98 ... ok
6/99 ... ok
6/100 ... ok
13/101 ... ok
13/102 ... ok
6/103 ... ok
18/104 ... ok
18/105 ... ok
18/106 ... ok
18/107 ... ok
18/108 ... ok
18/109 ... ok
18/110 ... ok
18/111 ... ok
6/112 ... ok
17/113 ... ok
15/114 ... ok
17/115 ... ok
9/116 ... ok
17/117 ... ok
12/120 ... ok
12/121 ... ok
17/122 ... ok
13/123 ... ok
12/124 ... ok
12/125 ... ok
10/126 ... ok
25/127 ... ok
21/128 ... ok
21/129 ... ok
17/130 ... ok
18/131 ... ok
6/132 ... ok
21/133 ... ok
24/134 ... ok
17/136 ... ok
12/137 ... ok
17/138 ... ok
17/139 ... ok
17/140 ... ok
13/141 ... ok
17/142 ... ok
17/143 ... ok
6/144 ... ok
17/145 ... ok
12/146 ... ok
6/147 ... ok
6/148 ... ok
12/149 ... ok
12/150 ... ok
17/151 ... ok
12/152 ... ok
13/153 ... ok
17/154 ... ok
9/155 ... ok
25/156 ... ok
12/157 ... ok
12/158 ... ok
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Redis available via internal API: OK

Access to /var/opt/gitlab/.ssh/authorized_keys: OK
gitlab-shell self-check successful

Checking GitLab Shell ... Finished

Checking Sidekiq ...

Running? ... yes
Number of Sidekiq processes ... 1

Checking Sidekiq ... Finished

Reply by email is disabled in config/gitlab.yml
Checking LDAP ...

LDAP is disabled in config/gitlab.yml

Checking LDAP ... Finished

Checking GitLab ...

Git configured correctly? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... yes
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory exists? ... yes
Uploads directory has correct permissions? ... yes
Uploads directory tmp has correct permissions? ... no
  Try fixing it:
  sudo chown -R git /var/opt/gitlab/gitlab-rails/uploads
  sudo find /var/opt/gitlab/gitlab-rails/uploads -type f -exec chmod 0644 {} \;
  sudo find /var/opt/gitlab/gitlab-rails/uploads -type d -not -path /var/opt/gitlab/gitlab-rails/uploads -exec chmod 0700 {} \;
  For more information see:
  doc/install/installation.md in section "GitLab"
  Please fix the error above and rerun the checks.
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
Projects have namespace: ... 
9/2 ... yes
8/4 ... yes
8/5 ... yes
7/6 ... yes
10/7 ... yes
7/8 ... yes
2/9 ... yes
9/10 ... yes
10/12 ... yes
10/13 ... yes
10/15 ... yes
10/16 ... yes
10/17 ... yes
10/19 ... yes
10/21 ... yes
10/22 ... yes
10/23 ... yes
10/24 ... yes
10/25 ... yes
10/26 ... yes
11/28 ... yes
11/29 ... yes
11/30 ... yes
7/31 ... yes
17/32 ... yes
17/33 ... yes
13/34 ... yes
13/35 ... yes
13/36 ... yes
6/37 ... yes
6/38 ... yes
6/39 ... yes
12/40 ... yes
12/41 ... yes
12/42 ... yes
12/43 ... yes
13/44 ... yes
6/45 ... yes
17/46 ... yes
13/47 ... yes
6/48 ... yes
8/49 ... yes
17/50 ... yes
6/51 ... yes
7/52 ... yes
7/53 ... yes
7/54 ... yes
13/55 ... yes
13/56 ... yes
6/57 ... yes
10/58 ... yes
12/59 ... yes
12/60 ... yes
17/61 ... yes
13/62 ... yes
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12/64 ... yes
17/65 ... yes
17/66 ... yes
17/67 ... yes
18/68 ... yes
17/70 ... yes
6/74 ... yes
25/75 ... yes
9/76 ... yes
9/77 ... yes
13/79 ... yes
13/80 ... yes
9/81 ... yes
6/82 ... yes
16/83 ... yes
13/84 ... yes
6/85 ... yes
13/86 ... yes
16/87 ... yes
13/88 ... yes
17/89 ... yes
17/90 ... yes
6/91 ... yes
12/92 ... yes
6/93 ... yes
17/94 ... yes
16/95 ... yes
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6/98 ... yes
6/99 ... yes
6/100 ... yes
13/101 ... yes
13/102 ... yes
6/103 ... yes
18/104 ... yes
18/105 ... yes
18/106 ... yes
18/107 ... yes
18/108 ... yes
18/109 ... yes
18/110 ... yes
18/111 ... yes
6/112 ... yes
17/113 ... yes
15/114 ... yes
17/115 ... yes
9/116 ... yes
17/117 ... yes
12/120 ... yes
12/121 ... yes
17/122 ... yes
13/123 ... yes
12/124 ... yes
12/125 ... yes
10/126 ... yes
25/127 ... yes
21/128 ... yes
21/129 ... yes
17/130 ... yes
18/131 ... yes
6/132 ... yes
21/133 ... yes
24/134 ... yes
17/136 ... yes
12/137 ... yes
17/138 ... yes
17/139 ... yes
17/140 ... yes
13/141 ... yes
17/142 ... yes
17/143 ... yes
6/144 ... yes
17/145 ... yes
12/146 ... yes
6/147 ... yes
6/148 ... yes
12/149 ... yes
12/150 ... yes
17/151 ... yes
12/152 ... yes
13/153 ... yes
17/154 ... yes
9/155 ... yes
25/156 ... yes
12/157 ... yes
12/158 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.3.5 ? ... yes (2.4.4)
Git version >= 2.9.5 ? ... yes (2.18.0)
Git user has default SSH configuration? ... yes
Active users: ... 5

Checking GitLab ... Finished

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)