In version v1.13.1 I noticed EZEE-1866 was fixed but It looks like the Map\Host is not working with multisite.

Steps to reproduce:

1. Prepare two separate domains.
2. Create two siteaccesses. Use Map\Host siteaccess matcher, and point each siteacess to separate domain. Remember to set multidomain_access() in the template, as described here: https://doc.ezplatform.com/en/1.13/guide/siteaccess/#map92host.
3. Configure content.tree_root.location_id for each siteaccess (might be the same for both)
4. Go to the Page mode.
5. Try to edit a Landing Page. You should notice, that the URL in browser address bar has been changed to /ez#/studio/insite/undefined.

You won't be able to edit landing page. Every attempt will end-up with an infinitive spinner.