I took another pass. Most all of them should be there now, minus a few where the example drafts weren't saved. I'll try to get the remainder by the end of the day.
It's highly recommended that you do not use GTM for munchkin on your Marketo LPs. You will lose the ability to filter web page visits on your landing pages names if you do so.
The template ID is a parameter passed in the body as "template", not as a path parameter. There were some examples on this page that somehow went unpublished here. I've published t...
Are you sure that you're impersonating the same record between the preview and the sample? Different numbers of available records would change the outcome of the rendering.
Try downloading the HTML of the Email and doing a full text search for "{{", that should show you all of the tokens it's attempting to parse and see which one is incorrect. Failing...