Reusable block inside query loop

Hi.

I’ve tried to create a reusable template inside a query loop. The only way I could find that seems to work is to group the items to be displayed in the level under the post template, and turn that group into a reusable block.

However, the moment I do that in the editor, my server grinds to a halt as long as that page or any preview of that page is open.

Is there a way to do this that works?

Thanks!