Steps to reproduce

1. Create and publish new Landing Page
2. Go to Content view, open Landing Page created in the previous step
3. Switch to Page
4. Switch to Edit mode
5. Do nothing. Just click on browser's back button
6. Browser should switch back to View mode (in Page Builder)
7. Switch to Edit mode again. From version popup select existing draft
8. Try to discard draft

Result
User will be redirected to 404 page with error message like:

Could not find Page for 'contentId: 76, versionNo: 2, languageCodes: [eng-GB]'