Steps to reproduce:
1. Set up HTTPS to portal
2. Start up portal
3. Go to Content > Forms
4. Add a Form
5. Add two fields and wait for autosave
Autosave would be triggered and user would continue building form.
When autosave is triggered, the form is reloaded and all info is vanished.
Note for developers:
Hot fixed on forms.liferay.com, but still reproducible on master.
It happens because RequestURL and ResponseURL are not always equal in the AutoSave's callback on form_portlet.js.