Magento 2.4.6: ValueError DOMDocument::loadXML() Argument #1 ($source) must not be empty when rendering notification_area UI component

I'm encountering a critical error in my Magento 2.4.6-p13 installation when the admin panel tries to render the notification area. The error appears in the exception logs but doesn't always break the page - it seems intermittent.

Error Details

[2025-11-19T07:07:44.087321+00:00] main.CRITICAL: ValueError: DOMDocument::loadXML(): Argument #1 ($source) must not be empty in /var/www/html/vendor/magento/framework/View/Element/UiComponent/Config/DomMerger.php:322
Stack trace:
#0 /var/www/html/vendor/magento/framework/View/Element/UiComponent/Config/DomMerger.php(322): DOMDocument->loadXML('')
#1 /var/www/html/vendor/magento/framework/View/Element/UiComponent/Config/DomMerger.php(391): Magento\Framework\View\Element\UiComponent\Config\DomMerger->createDomDocument('')
#2 /var/www/html/vendor/magento/framework/View/Element/UiComponent/Config/Reader.php(60): Magento\Framework\View\Element\UiComponent\Config\DomMerger->merge('')
#3 /var/www/html/vendor/magento/framework/View/Element/UiComponent/Config/Reader.php(47): Magento\Framework\View\Element\UiComponent\Config\Reader->readFiles(Array)
#4 /var/www/html/vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php(121): Magento\Framework\View\Element\UiComponent\Config\Reader->__construct(Object(Magento\Framework\View\Element\UiComponent\Config\FileCollector\AggregatedFileCollector), Object(Magento\Framework\View\Element\UiComponent\Config\Converter), Object(Magento\Framework\View\Element\UiComponent\Config\DomMerger))
#5 /var/www/html/vendor/magento/framework/ObjectManager/Factory/Compiled.php(108): Magento\Framework\ObjectManager\Factory\AbstractFactory->createObject('Magento\\Framewo...', Array)
#6 /var/www/html/vendor/magento/framework/ObjectManager/ObjectManager.php(56): Magento\Framework\ObjectManager\Factory\Compiled->create('Magento\\Framewo...', Array)
#7 /var/www/html/vendor/magento/framework/View/Element/UiComponent/Config/ReaderFactory.php(40): Magento\Framework\ObjectManager\ObjectManager->create('Magento\\Framewo...', Array)
#8 /var/www/html/vendor/magento/framework/View/Element/UiComponent/Config/Provider/Template.php(105): Magento\Framework\View\Element\UiComponent\Config\ReaderFactory->create(Array)
#9 /var/www/html/vendor/magento/framework/View/TemplateEngine/Xhtml.php(78): Magento\Framework\View\Element\UiComponent\Config\Provider\Template->getTemplate(false)
#10 /var/www/html/vendor/magento/framework/View/Element/UiComponent/ContentType/Xml.php(66): Magento\Framework\View\TemplateEngine\Xhtml->render(Object(Magento\Ui\Component\Listing), false)
#11 /var/www/html/vendor/magento/module-ui/Component/AbstractComponent.php(158): Magento\Framework\View\Element\UiComponent\ContentType\Xml->render(Object(Magento\Ui\Component\Listing), 'templates/listi...')
#12 /var/www/html/vendor/magento/module-ui/Component/Wrapper/UiComponent.php(72): Magento\Ui\Component\AbstractComponent->render()
#13 /var/www/html/vendor/magento/framework/View/Element/AbstractBlock.php(1128): Magento\Ui\Component\Wrapper\UiComponent->_toHtml()
#14 /var/www/html/vendor/magento/framework/View/Element/AbstractBlock.php(1132): Magento\Framework\View\Element\AbstractBlock->Magento\Framework\View\Element\{closure}()
#15 /var/www/html/vendor/magento/framework/View/Element/AbstractBlock.php(676): Magento\Framework\View\Element\AbstractBlock->_loadCache()
#16 /var/www/html/generated/code/Magento/Ui/Component/Wrapper/UiComponent/Interceptor.php(23): Magento\Framework\View\Element\AbstractBlock->toHtml()
#17 /var/www/html/vendor/magento/framework/View/Layout.php(591): Magento\Ui\Component\Wrapper\UiComponent\Interceptor->toHtml()
#18 /var/www/html/vendor/magento/framework/View/Layout.php(553): Magento\Framework\View\Layout->_renderUiComponent('notification_ar...')
#19 /var/www/html/vendor/magento/framework/View/Layout.php(510): Magento\Framework\View\Layout->renderNonCachedElement('notification_ar...')
#20 /var/www/html/vendor/magento/framework/View/Layout.php(606): Magento\Framework\View\Layout->renderElement('notification_ar...', false)
#21 /var/www/html/vendor/magento/framework/View/Layout.php(557): Magento\Framework\View\Layout->_renderContainer('notifications', false)
#22 /var/www/html/vendor/magento/framework/View/Layout.php(510): Magento\Framework\View\Layout->renderNonCachedElement('notifications')
#23 /var/www/html/vendor/magento/framework/View/Layout.php(606): Magento\Framework\View\Layout->renderElement('notifications', false)
#24 /var/www/html/vendor/magento/framework/View/Layout.php(557): Magento\Framework\View\Layout->_renderContainer('notices.wrapper', false)
#25 /var/www/html/vendor/magento/framework/View/Layout.php(510): Magento\Framework\View\Layout->renderNonCachedElement('notices.wrapper')
#26 /var/www/html/vendor/magento/framework/View/Layout.php(606): Magento\Framework\View\Layout->renderElement('notices.wrapper', false)
#27 /var/www/html/vendor/magento/framework/View/Layout.php(557): Magento\Framework\View\Layout->_renderContainer('page.wrapper', false)
#28 /var/www/html/vendor/magento/framework/View/Layout.php(510): Magento\Framework\View\Layout->renderNonCachedElement('page.wrapper')
#29 /var/www/html/vendor/magento/framework/View/Layout.php(606): Magento\Framework\View\Layout->renderElement('page.wrapper', false)
#30 /var/www/html/vendor/magento/framework/View/Layout.php(557): Magento\Framework\View\Layout->_renderContainer('backend.page', false)
#31 /var/www/html/vendor/magento/framework/View/Layout.php(510): Magento\Framework\View\Layout->renderNonCachedElement('backend.page')
#32 /var/www/html/vendor/magento/framework/View/Layout.php(606): Magento\Framework\View\Layout->renderElement('backend.page', false)
#33 /var/www/html/vendor/magento/framework/View/Layout.php(557): Magento\Framework\View\Layout->_renderContainer('root', false)
#34 /var/www/html/vendor/magento/framework/View/Layout.php(510): Magento\Framework\View\Layout->renderNonCachedElement('root')
#35 /var/www/html/vendor/magento/framework/View/Layout.php(975): Magento\Framework\View\Layout->renderElement('root')
#36 /var/www/html/generated/code/Magento/Framework/View/Layout/Interceptor.php(41): Magento\Framework\View\Layout->getOutput()
#37 /var/www/html/vendor/magento/framework/View/Result/Page.php(260): Magento\Framework\View\Layout\Interceptor->getOutput()
#38 /var/www/html/vendor/magento/framework/View/Result/Layout.php(171): Magento\Framework\View\Result\Page->render(Object(Magento\Framework\App\Response\Http\Interceptor))
#39 /var/www/html/generated/code/Magento/Backend/Model/View/Result/Page/Interceptor.php(23): Magento\Framework\View\Result\Layout->renderResult(Object(Magento\Framework\App\Response\Http\Interceptor))
#40 /var/www/html/vendor/magento/framework/App/Http.php(120): Magento\Backend\Model\View\Result\Page\Interceptor->renderResult(Object(Magento\Framework\App\Response\Http\Interceptor))
#41 /var/www/html/vendor/magento/framework/App/Bootstrap.php(264): Magento\Framework\App\Http->launch()
#42 /var/www/html/pub/index.php(30): Magento\Framework\App\Bootstrap->run(Object(Magento\Framework\App\Http\Interceptor))
#43 {main} {"exception":"[object] (ValueError(code: 0): DOMDocument::loadXML(): Argument #1 ($source) must not be empty at /var/www/html/vendor/magento/framework/View/Element/UiComponent/Config/DomMerger.php:322)"} []
[2025-11-19T07:07:44.625824+00:00] main.CRITICAL: ValueError: DOMDocument::loadXML(): Argument #1 ($source) must not be empty in /var/www/html/vendor/magento/framework/View/Element/UiComponent/Config/DomMerger.php:322
Stack trace:

Context

• Magento Version: 2.4.6-p13
• PHP Version: 8.2
• Error occurs: When rendering admin notification area UI component
• Frequency: Intermittent - appears multiple times in logs.

What I've Tried

1. Searched for empty/malformed XML files:

   find app/code -path "*/ui_component/*.xml" -type f -exec sh -c 'if [ $(wc -c < "$1") -lt 100 ]; then echo "$1"; fi' _ {} \;
   

   No unusually small files found.

2. Checked for custom overrides:

   grep -r "notification_area" app/code --include="*.xml"
   grep -r "notification_area" app/design --include="*.xml"
   

   No custom overrides of notification_area.xml found.

3. Verified core file exists and is valid:

   cat vendor/magento/module-admin-notification/view/adminhtml/ui_component/notification_area.xml
   

   File exists and contains valid XML with proper <listing> structure.

4. Checked for broken symlinks:

   find app/code -path "*/ui_component/*.xml" -type l
   

   No broken symlinks found.

Analysis

The stack trace shows:

• DomMerger->merge('') is being called with an empty string at line #2
• This happens during Reader->readFiles(Array) at line #3
• The AggregatedFileCollector must be collecting a file that returns empty content
• Specifically happening when rendering notification_area UI component

Questions

1. How can I debug which file is returning empty content to the FileCollector? The readFiles() method receives an array of files - how do I log/inspect this array?

2. Is this a known caching issue? Would clearing var/cache, var/page_cache, var/view_preprocessed, and generated/* resolve this?

3. Could this be caused by a disabled module that previously declared a UI component extension that's now referenced but file doesn't exist?

4. What's the proper way to trace the UI component file collection process to find the problematic file?

Environment Details

• Running in Docker with PHP-FPM 8.2
• 60+ custom modules under app/code/
• Custom admin theme at app/design/adminhtml/
• No recent module enable/disable changes

What I Need

A systematic approach to:

1. Identify which file path is returning empty content
2. Understand why the FileCollector is including a non-existent or empty file
3. Prevent this error from recurring after fix

Any guidance on debugging Magento 2's UI Component file collection and merging process would be greatly appreciated.