Gabriela Anechitoaei I think you're mixing two things here:

• when you edit again, the checkbox is unchecked although realtime collaboration is active -> this is a bug, and I'm going to push the fix after 16.3RC1
• when you edit again, realtime collaboration is enabled although you previously, in a different editing session, chose to leave the realtime -> this is an improvement: remember the choice of editing in realtime or not for the next editing sessions; ATM realtime is always enabled when you enter edit mode if the realtime plugin is enabled in the CKEditor administration.

Note that for the second item I could easily use the browser local storage to remember the state of the "Allow realtime collaboration" but this will create problems with the edit lock check (XWIKI-21625) that Dorian Ouakli is working on because he currently assumes that if there is an active realtime session you will automatically join it. But that will not be true anymore if we remember that you left the realtime session only on the client side (browser). The server needs to know also, so that you get the edit lock confirmation when editing again, if another user has started editing in the meantime (even if that user has realtime enabled).