Looks like the permissions are only set to edit and not create.

if ($input->get('view') === 'article' && $input->get('layout') === 'pagebreak')
{
    if (!$user->authorise('core.edit', 'com_content'))
    {
        JFactory::getApplication()->enqueueMessage(JText::_('JERROR_ALERTNOAUTHOR'), 'warning');

        return;
    }
}

That should be easy to correct

the problem is also for "Article" button in the editor

yes

elseif ($input->get('view') === 'articles' && $input->get('layout') === 'modal')
{
    if (!$user->authorise('core.edit', 'com_content'))
    {
        JFactory::getApplication()->enqueueMessage(JText::_('JERROR_ALERTNOAUTHOR'), 'warning');

        return;
    }
}

in the same file
ROOT/components/com_content/content.php

You do PR or I do?

hmm, wondering now if that was on purpose...
Did it work OK before 3.6.2?

This code was added in 3.4.5
dca641f#diff-35390bcd97e9f612d6fc06ea874aa22a

@wilsonge
As you did that commit, could you give us some infos?

I think it should be like this:

• allowed to core.edit and item id different than 0: Allowed
• allowed to core.edit.own, item created by user and item id different than 0: Allowed
• allowed to core.create and item id equal to 0: Allowed
• else: Not allowed

and IMHO this should be applied to all components with modals.

But it's better for @wilsonge to confirm there is no problem with that.

Also the warning should IMHO be a 403 exception

throw new JAccessExceptionNotallowed(JText::_('JERROR_ALERTNOAUTHOR'), 403);

For your info, that code was added for security reasons at the time.
One of the issues with letting people display the modals with Create or Edit own only is that they will be able to see in the modals titles of stuff they may not be allowed to see (access restricted): Articles, menu items, contacts.
For pagebreak, indeed, no use imho to restrict to edit.

For pagebreak, indeed, no use imho to restrict to edit.

Yes, and this is issue is a kind of duplicate,

There is already a discussion here: #10653

Please see my comment: #10653 (comment)

Please see also
#12321 (comment)

See PR here
#12353

Closed as we have a PR - thanks