To solve this problem please take the following steps:
1. Open builder in Chrome or Firefox browser
2. Open developer tools in browser (key F12)
3. Switch to “Network” tab
4. Click on “Save” button in builder
5. Click on appeared request line (it should begin with “?sess=”)
6. Switch to “Response” tab
7. Copy text you see in this tab
8. Create ticket on site.pro and tell us about “error loading page” and paste copied text. Our developers will fix this problem.
9. Thank you and excuse us for inconvenience.