Unable to use squash commits on merge function

Summary

Whenever I check the squash commits on merge functionality and attempt to merge it will just hang forever.

Steps to reproduce

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

1. Go to a merge request

2. Check squash commits checkbox

3. Click Accept Merge Request

(What actually happens)

The merge request will not be merged in and just hangs

(What you should see instead)

The merge request will be merged into the appropriate branch and the commits will be squashed

Output of checks

This bug happens on GitLab.com