As a note, there can be a number of reasons why the editor goes unresponsive, if the Editor does go unresponsive and keeps happening, please get in contact with the Webflow support team at the contact page: Webflow Customer Support | Webflow University
Webflow support will do there best to assess what might be happening and to determine if the issue is site specific or a wider issue.
Custom code can also be a factor, usually custom code is disabled in the Editor mode, but occasionally some unique combination of design, custom code etc will raise exceptions.
Size of the site at the moment also is a factor, if there are heavy pages (lots of images, very large dom structure) and many CMS items with large data sets, this can also cause the editor to go unresponsive. Usually working in the browser with only a single browser tab open also helps.
The Webflow team is aware that there are these kinds of issues on some site projects, the overwhelming majority this does not happen, but anytime it happens is too often and work continues to eradicate this kind of behavior completely.
Updates continue to be made ensure a smooth experience, but please do contact Webflow support in case of issues like this so we can provide private account assistance, unresponsive editor issues is definitely within the scope of Webflow support and the whole team is here to help.