Well, we are currently testing OJS 3.3.0.11 on a test server by upgrading from 3.1.2.4. However, we had not defined the checklist in the previous version (I believe we were using the default checklist). In 3.3.0.11 we had trouble loading the checklist to modify it. We had to downgrade, manually define it in 3.1.2.4, and then upgrade again. Only then we were able to modify the checklist.
Check this other thread. Checklist stuck on Loading and they appear in Spanish in the submission form - #3 by agmarrugo