So i cannot save categories and attempting to do so produces below error in system.log:
(2021-04-15 16:16:30) main.CRITICAL: Error: Call to a member function getAttributeCode() on bool in /home/sites/buzzcateringsupplies.com/public_html/vendor/magento/module-catalog/Observer/InvalidateCacheOnCategoryDesignChange.php:67
Stack trace:
#0 /home/sites/magento/public_html/vendor/magento/framework/Event/Invoker/InvokerDefault.php(88): MagentoCatalogObserverInvalidateCacheOnCategoryDesignChange->execute(Object(MagentoFrameworkEventObserver))
...
...
Strange as seems to work in my dev environment so seems some update have not occured in live database when running setup upgrade. I notice that my custom layout update attribute is empty like below:

So i am assuming there are potentially a few things wrong here.
Other solutions suggest running queries like below in to database:
INSERT INTO `eav_attribute` (`entity_type_id`, `attribute_code`, `attribute_model`, `backend_model`, `backend_type`, `backend_table`, `frontend_model`, `frontend_input`, `frontend_label`, `frontend_class`, `source_model`, `is_required`, `is_user_defined`, `default_value`, `is_unique`, `note`) VALUES
(4, 'custom_layout_update_file', NULL, 'Magento\Catalog\Model\Product\Attribute\Backend\LayoutUpdate', 'varchar', NULL, NULL, 'select', 'Custom Layout Update', NULL, 'Magento\Catalog\Model\Product\Attribute\Source\LayoutUpdate', 0, 0, NULL, 0, NULL),
(3, 'custom_layout_update_file', NULL, 'Magento\Catalog\Model\Category\Attribute\Backend\LayoutUpdate', 'varchar', NULL, NULL, 'select', 'Custom Layout Update', NULL, 'Magento\Catalog\Model\Category\Attribute\Source\LayoutUpdate', 0, 0, NULL, 0, NULL);
However not a big fan and would like to get to bottom of why this update has not run. The above does actually allow saving of categories however the dropdown is still empty. I’m also confused as thought in 2.3.4 and above the Layout update XML field should no longer be present…
Have searched around and cannot see a solution or explanation and hoping someone might be able to point me in the right direction. Have tried a few DB imports and updates since however same thing happens.