### Summary <!-- Summarize the bug encountered concisely. --> When creating a merge request from my fork [`KevSlashNull/gitlab`](https://gitlab.com/KevSlashNull/gitlab) targeted at `gitlab-org/gitlab`, I frequently encounter an Error 500 page (latest example, 3 or 4 retries: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/66691). I’ve been experiencing this for at least half a year but recently it’s been worse. ### Steps to reproduce <!-- Describe how one can reproduce the issue - this is very important. Please use an ordered list. --> Create a merge request from my fork? Maybe any fork of the `gitlab` project is impacted by this. ### Example Project <!-- If possible, please create an example project here on GitLab.com that exhibits the problematic behavior, 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 is fixed in a more recent version. --> :point_right: https://gitlab.com/KevSlashNull/gitlab ### What is the current *bug* behavior? <!-- Describe what actually happens. --> Most of the time when creating a merge request, the request fails after around 55s with an error 500 **without creating the merge request**. Trying to resubmit will likely cause the error, although after a few retries, the merge request will be created and you will be redirected. ### What is the expected *correct* behavior? <!-- Describe what you should see instead. --> I can create a valid merge request from a fork at the upstream project without any errors. ### Relevant logs and/or screenshots <!-- Paste any relevant logs - please use code blocks (```) to format console output, logs, and code as it's tough to read otherwise. -->  #### Hopefully relevant HTTP response headers ``` date: Thu, 22 Jul 2021 23:07:14 GMT gitlab-lb: fe-18-lb-gprd gitlab-sv: web-cny-03-sv-gprd x-request-id: 01FB87GDK174XXNKWGQDBE93W8 x-runtime: 57.195001 ``` ### Output of checks <!-- If you are reporting a bug on GitLab.com, write: This bug happens on GitLab.com --> This bug happens on GitLab.com #### Results of GitLab environment info <!-- Input any relevant GitLab environment information if needed. --> <details> <summary>Expand for output related to GitLab environment info</summary> <pre> (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`) </pre> </details> #### Results of GitLab application Check <!-- Input any relevant GitLab application check information if needed. --> <details> <summary>Expand for output related to the GitLab application check</summary> <pre> (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) </pre> </details> ### Possible fixes <!-- If you can, link to the line of code that might be responsible for the problem. -->