Unable to apply a template using rich text editor on specific projects

Summary

On https://gitlab.com/gitlab-org/gitlab-design while applying any template while still using rich text editor, the following error pops up:

This goes away when we toggle to plain text editor.

Steps to reproduce

Go to the project https://gitlab.com/gitlab-org/gitlab-design and try to create a new issue by applying the “Product Designer Onboarding” template, while still using rich text editor.

Example Project

What is the current bug behavior?

Unable to apply the template without switching to plain text editor.

What is the expected correct behavior?

Should be able to switch to apply the template easily.

Relevant logs and/or screenshots

Output of checks

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