Error message on uploading images

I get the message on unexpected places as well.

Even though the node itself has been successfully locked, once I open a previously closed table paragraph, the module error message appears.

Does it, by any chance, try to lock all loaded entitys when you are in the backend?

Seems to me like this happens whenever an AJAX callback is issued to refresh a part of the form which gets rebuilt, which triggers content_lock_node_form_handler() for acquiring a lock on the node edit form.
That fails because there's no token provided by the AJAX call, and because of that an error message is returned by the AJAX call, and displayed on the page where the area is refreshed.

I'm not quite sure my approach is the right one but here is a patch suggestion attached.
It solves the issue in our scenario, but I'm wondering if it doesn't bypass some of this module's security layers somehow, as it now skips locking in this particular case:
* Current user already has a lock on the node's form being processed
* The form is being rebuilt ($form_state['rebuild'] == TRUE)

Same patch, simply moved the code further up in the function, as it did not need to run that late.

The patch works for me. The error when I open paragraphs and the callback is triggered does not cause the "content could not be locked" error anymore.

About the security implications ... my understanding is (please correct me if I'm wrong about it) that since the user already has a lock on a node, the module doesnt need to lock the node anew just because a form rebuild was triggered.

Patch #5 is also successfully solving the issue for me. It happened with every ajax related form updates, like image upload, paragraphs, inline_entity_forms and co. So it should affect a lot of users.

Update: I've noticed recently that the last patch causes paragraphs to be saved when node edit is cancelled.

Though I have absolutely no clue why this happens at all. Can someone else verify this behaviour?