Any messages in the log file?

or in HTL/Sightly:${inheritedPageProperties.foo}

For every implementation make sure all the output is escaped in the correct way.Here a sheet with XSS examples: https://docs.adobe.com/docs/en/cq/5-6-1/developing/securitychecklist/_jcr_content/par/download/file.res/xss_cheat_sheet.pdf

What you can consider too, is to disable minify on publish. And to do this on Apache.

Tried indeed several things, but it isn't working..What about creating a use-class that converts the String to a Map?Then your integration can stay as is.

Sorry missed you final sentence Can you try @ context = 'unsafe'?

Have a look at data-sly-attribute, you can pass in a map.https://docs.adobe.com/docs/en/htl/docs/block-statements.html

Look at the design-importer feature, this seems what you are looking for.

what do you mean with "saved as nodes"

Looks like you are using invalid tags, anyway we can reproduce this?