User error: "attributes" is an invalid render array key when rendering image
Yes, it seems like you are not supposed to render item in a field template. Render item.attributes and item.content separately:

&lt;div{{ item.attributes }}&gt;{{ item.content }}&lt;/div&gt;


Or the attributes in a &lt;span&gt; if the &lt;div&gt; doesn't work with your layout and you need the attributes:

&lt;span{{ item.attributes }}&gt;{{ item.content }}&lt;/span&gt;


BTW storage' =&gt; [] is part of the Attribute object any code can store attributes on its way until it reaches your template. So it's a good idea to print the attributes, even if they are now empty, because you don't know which extension you might want to install in the future and debugging will then be some fun until you'll find out that one of the field templates is not fully working.