Hey @ChristianV, I just gave this a go on my end and it seems n8n doesn’t like a string in the headers field for your first example. Looks like a small bug to me and I’ll take a closer look into this when I have a bit more time.
As a quick workaround I was however able to just return a JSON object through an expression like so:
Could you give this a go on your end and see if this does the trick for you as well?