Page editing conflict choices don't work if the page edit is made in-place

STEPS TO REPRODUCE

1. Login as Admin and create an user (e.g. U1)
2. Edit a page with in-place editor (insert e.g. 'edit1')
3. Click 'Save'
4. Open a different browser (or an incognito window) and login with the user (U1)
5. Go to the same page and (force) edit it also with in-place editor (insert e.g. 'edit2')
6. Click 'Save'
7. Go to the browser where Admin is logged in and type a word (e.g. 'edit3')
8. Click 'Save'
9. Select 'Fix each conflict individually'
10. On the bottom, select each option from the drop-down: 'your current changes', 'before your changes', 'latest version saved', 'custom version'

EXPECTED RESULTS

For each selected drop-down option, the content is displayed accordingly in the left side, so the user can choose what to save.

ACTUAL RESULTS

When selecting a choice, the content displayed on the left side is not changing and it seems that many values are displayed at once.

I've tested also by editing both pages with Wysiwyg editor and it works properly.