vaadin-grid TypeError

I am trying to use vaadin-grid to create a table using iron-ajax. A lot of TypeErrors result:

Uncaught TypeError: Polymer.dom(…).querySelectorAll(…).filter is not a function
Uncaught TypeError: Cannot read property ‘forEach’ of undefined
Uncaught TypeError: Cannot read property ‘length’ of undefined

I am sure the iron-ajax is loaded as I have tested this by printing the data.

<iron-ajax auto url="../../static/data/parameters.json" last-response="{{params}}" handle-as="json"></iron-ajax>

<vaadin-grid items="[[params]
  <vaadin-grid-column width="50px" flex-grow="0">
    <template class="header">Parameter</template>

The problem seemed to be with my package installs. Reinstalling all bower packages fixed the problem.

I am using the Grid component. I setup the grid with this:


This addColumn call created JS TypeError in Google Chrome:
client-28831013082792340517B7074033EF04.cache.js:198 (TypeError) : $0.$connector.setColumnId is not a function.

Any suggestion?