Merge Request page returns error 500 on gitlab.com

Summary

When going to Merge Request page, the request takes a very long time and eventually returns Error 500.

Steps to reproduce

When going to Merge Request page, e.g. https://gitlab.com/appstart-lt/baltic-brows-rn/merge_requests/85, the request takes a very long time and eventually returns Error 500. This happens only with one of my projects, though with any of its merge requests. All other projects and their merge requests load perfectly fine. I use Gitlab hosted on gitlab.com, tried Next, but still the same error is returned.

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)

What is the current bug behavior?

Merge Request page returns server error 500.

What is the expected correct behavior?

Merge Request page loaded without any errors.

Relevant logs and/or screenshots

Output of checks

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)

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)

Possible fixes

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