The realtime WYSIWYG editor remains stuck on "Connecting" after reconnecting when it was the only one editing

We hit this on XWiki 18.7.0 (CKEditor realtime WYSIWYG, single node, behind an Azure Application Gateway; netflux idle timeout raised to 240 s locally as a workaround for XWIKI-24799). In our case it causes loss of the user's work, so it is more than a UI hang.

Sequence, from server DEBUG logs (org.xwiki.netflux) and the user's browser console, sole editor:

1. The user enters in-place edit; the netflux session joins the editor's three channels and edits reach the server.
2. The WebSocket is closed abruptly (EOFException on the server, last message received 10 ms earlier; in our case caused by a network event).
3. 7 s later the browser reconnects with a new netflux session and tries to JOIN one of the old channels; the server answers ERROR ENOENT, because the channels were removed when their only member left.
4. The client never rejoins. The socket stays open (pings are acknowledged), but every change is rejected client-side: the console fills with {{ {type: 'NO_SUCH_CHANNEL', message: '[1485,"MSG","<old channel id>",…]'}

   }} from wysiwygEditor.js:905, with the sequence number increasing on each attempt. Nothing reaches the server, and no save request (manual or automatic) arrives either.

5. The editor stays disconnected; the user reloads and loses everything typed after step 2.

In a week with frequent connection drops (an infrastructure issue on our side, since fixed) we saw 11 editing sessions end in this state. Nearly all our realtime sessions have a single editor, so any connection drop while editing puts that user's work at risk.

Expected: when the old channel no longer exists, re-create or rejoin it with the client's current state (as suggested in the description: refresh the channel keys on reconnect), or at least stop and tell the user to copy their content and reload, instead of silently dropping changes.

Workaround we applied: disabled the xwiki-realtime CKEditor plugin. Happy to provide sanitized logs.