Contents disappeared when we check 'Allow Realtime Collaboration' input

I have installed the xwiki-enterprise-jetty-hsqldb-7.1.2

• Connect with Admin accont
• Install the following extensions :
  • Realtime Collaborative Plain WikiText Editor 1.10
  • Visual Realtime Collaborative Editor (EXPERIMENTAL)
• Create a new user (UserTest/UserTest )
• Add the admin right to the UserTest
• Connect with UserTest on new browser
• Create a new page ( XWiki.TestRealtimeCollaboration ) with UserTest , save and view it
• Edit the page with Admin
• With UserTest edit the page and join the realtime collaboration, then do the following :
  • Add 'Some text User' With UserTest account
  • unCheck the input "Allow Realtime Collaboration"
  • The check it again
    Result the text 'Some text User' will be removed