Editing a checklist race condition

Summary

Currently if you open 2 windows and edit an issue with a checklist and then complete an item in the checklist in a separate window, you'll lose any of the edits from the first session. Seems like a race condition.

Steps to reproduce

1. create issue with task list (markdown "- [ ]")
2. open this issue in two browser windows at the same time
3. edit issue in first browser window (add any new data) and save changes
4. don't refresh page in second browser
5. check in any checkbox in second browser

Expected behavior

The edits from the first browser window should be saved, and the checkmark should be saved.

Actual behavior

You'll lose the edits from the first window.

This bug happens on GitLab.com