Query XML for Repeating Section - how to set up correctly?

This has been discussed ad nauseum in countless threads, but I cannot for the life of me find how to correctly provision the workflow to iterate through the collection.

Let's say I have a repeating section with a single text field that a user can add to.

The xml will look like this, in my RepeatingSection column (plain text, multiline):

<?xml version="1.0" encoding="utf-8"?>

<RepeaterData><Version />

<Items>

<Item><Thing type="System.String">First thing</Thing></Item>

<Item><Thing type="System.String">Second thing</Thing></Item>

<Item><Thing type="System.String">Third thing</Thing></Item>

</Items>

</RepeaterData>

I know I need to use Query XML to get the collection information, but I don't know how to set it up correctly. I can drill down to the "Thing" item that I want, but do I keep the [1] as the index when initially querying? If I set it to a WF variable, it doesn't work.

Here are my variables:

My For each loop performs a Collection operation to Get items from the collection (at least that's the idea)

Here is the For each:

And the Collection operation:

Which should update another plain multiline with the Thing(s) texts:

Except it only grabs the first item, which is "First thing" and helpfully logs: "Index 0 has thing First thing" which is correct but not exactly what I want. 

Why is it not looping through the collection?