Cannot edit pages

For some time we haven’t been able to edit text on several pages. When clicking the “edit” button a window opens up with a little wheel spinning and nothing happens even after waiting several minutes.
For some reason, the main page (https://www.vikingscubakabira.com/en) is working fine but almost all other pages have this problem. We tried both the frontend and the backend editor and have the latest version installed.

Since it’s possible to create new text blocks we currently work around it by doing that every time we have to edit but it’s a bit annoying.

The page I need help with: [log in to see the link]