After upgrade Magento to version 2.4.5 you can see this error: TypeError: Magento\Elasticsearch\Model\ResourceModel\Fulltext\Collection\SearchResultApplier::categoryProductByCustomSortOrder(): Argument #1 ($categoryId) must be of type int, array given
This bug is related to the latest Magento changes and custom extensions like Amasty Improved Layered Navigation.
To see more information
If you are Amasty customer, you can fix this error by installing additional package from our private repository:
composer require amasty/module-mage-2.4.5-fix
But this case can be reproduced without our extension. This is why we made this package public.