Flex Gumbo SDK Iteration 10 FXG has an issue with the Repeater object the content property is not binding, I submited a ticket to Adobe here.

The code that repoduce the error is below:

   <mx:Repeater id="r" dataProvider="{ar}">
<FxButton left="20" top="335" content="{r.currentItem}" skinClass="components.Button" />
    </mx:Repeater> 

I couldn’t find any workaround and end up using the ‘DataGroup’ FXG object instead. The DataGroup allow you to do what the repeater does so I am not going to be surprised if Adobe decide to deprecate the component.

    <DataGroup>
        <layout><VerticalLayout gap="1" /></layout>
        <dataProvider>
            <ArrayCollection>
				<FxButton id="btn4" left="20" top="335" content="{arrayCollection.getItemAt(0)}"
					skinClass="components.Button" includeIn="SearchPage" />
            </ArrayCollection>
        </dataProvider>
    </DataGroup>

Or you can set the array collection as any component and attach it;

<DataGroup dataProvider="{arrayCollection}" />