Hi all,
It was upgrade time to J4 from 3.10.12 website.
It's seems all ok (only a plugin with error now disabled),
BUT
in the backend it's no possible edit articles or old-modules, create a new article.
It's coming 500 500 behavior::modal not found.

With error log active this is an example:

Call stack

Function Location

1 () JROOT/libraries/src/HTML/HTMLHelper.php:141
2 Joomla\CMS\HTML\HTMLHelper::_() JROOT/plugins/editors-xtd/ggpkg_editor/ggpkg_editor.php:46
3 plgButtonggpkg_editor->onDisplay() JROOT/libraries/src/Editor/Editor.php:236
4 Joomla\CMS\Editor\Editor->getButtons() JROOT/libraries/src/Editor/Editor.php:96
5 Joomla\CMS\Editor\Editor->Joomla\CMS\Editor{closure}() JROOT/libraries/vendor/joomla/event/src/Dispatcher.php:486
6 Joomla\Event\Dispatcher->dispatch() JROOT/plugins/editors/codemirror/src/Extension/Codemirror.php:292
7 Joomla\Plugin\Editors\CodeMirror\Extension\Codemirror->displayButtons() JROOT/plugins/editors/codemirror/src/Extension/Codemirror.php:146
8 Joomla\Plugin\Editors\CodeMirror\Extension\Codemirror->onDisplay() JROOT/libraries/src/Editor/Editor.php:195
9 Joomla\CMS\Editor\Editor->display() JROOT/libraries/src/Form/Field/EditorField.php:250
10 Joomla\CMS\Form\Field\EditorField->getInput() JROOT/libraries/src/Form/FormField.php:471
11 Joomla\CMS\Form\FormField->get() JROOT/libraries/src/Form/Field/TextareaField.php:94
12 Joomla\CMS\Form\Field\TextareaField->get() JROOT/libraries/src/Form/Field/EditorField.php:138
13 Joomla\CMS\Form\Field\EditorField->__get() JROOT/libraries/src/Form/Form.php:458
14 Joomla\CMS\Form\Form->getInput() JROOT/administrator/components/com_content/tmpl/article/edit.php:72
15 include() JROOT/libraries/src/MVC/View/HtmlView.php:415
16 Joomla\CMS\MVC\View\HtmlView->loadTemplate() JROOT/libraries/src/MVC/View/HtmlView.php:203
17 Joomla\CMS\MVC\View\HtmlView->display() JROOT/administrator/components/com_content/src/View/Article/HtmlView.php:116
18 Joomla\Component\Content\Administrator\View\Article\HtmlView->display() JROOT/libraries/src/MVC/Controller/BaseController.php:660
19 Joomla\CMS\MVC\Controller\BaseController->display() JROOT/administrator/components/com_content/src/Controller/DisplayController.php:64
20 Joomla\Component\Content\Administrator\Controller\DisplayController->display() JROOT/libraries/src/MVC/Controller/BaseController.php:693
21 Joomla\CMS\MVC\Controller\BaseController->execute() JROOT/libraries/src/Dispatcher/ComponentDispatcher.php:143
22 Joomla\CMS\Dispatcher\ComponentDispatcher->dispatch() JROOT/libraries/src/Component/ComponentHelper.php:361
23 Joomla\CMS\Component\ComponentHelper::renderComponent() JROOT/libraries/src/Application/AdministratorApplication.php:143
24 Joomla\CMS\Application\AdministratorApplication->dispatch() JROOT/libraries/src/Application/AdministratorApplication.php:186
25 Joomla\CMS\Application\AdministratorApplication->doExecute() JROOT/libraries/src/Application/CMSApplication.php:293
26 Joomla\CMS\Application\CMSApplication->execute() JROOT/administrator/includes/app.php:61
27 require_once() JROOT/administrator/index.php:32

It seems possible to create a new module.

Any ideas about this issue?
Thanks.
M.