magento2 – Magento dom validation exception

I get this error on my product page and only for specific products.

Exception #0 (MagentoFrameworkConfigDomValidationException): Element 'handle': Character content other than whitespace is not allowed because the content type is 'element-only'.

The error is because the sku of the product is added in the layout xml like this:

<layout xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><handle id="handle">479259<body>

Here the number 479259 is the sku and this should not be there. I disabled all my custom modules, even changed my theme to the default magento theme, changed to production mode, changed my database (the one on production doesn’t give this error) but I still get this error. Is there any way to find out where this sku is coming from?

The error I get in one of the logs is:

Cache file with merged layout: LAYOUT_frontend_STORE1_4e763528242bc7a0eb065e4d209735c84_page_layout_merged and handles default, catalog_product_view, catalog_product_view_type_configurable, catalog_product_view_id_117064, catalog_product_view_sku_479259, pl_thm_customtheme_default, pl_thm_customtheme_default_default, cms_noroute_index, cms_page_view, cms_noroute_index_id_collection, amshopbybase_swiper: Please correct the XML data and try again. Element 'handle': Character content other than whitespace is not allowed because the content type is 'element-only'.

Thank you for the help!