@scarecroow If you’re wondering about inserting a repeater in a repeater, that is not supported, though it has been requested of the Wix development team.
So I’m clear about what I mean above, the only reason to initially insert the box on the page is because you will want to re-size it first so the dimensions fit the repeater row appropriately. Once you have that done, remove any elements you might already have in the repeater, and drag and drop the box onto the repeater item. Then if you had removed any items, add them back into the container box. Make sense?