Error: The node to be removed is not a child of this node: [object Text]

[Stefdv]

just copied your demo and get this error: "The node to be removed is not a child of this node: [object Text]"

 <zero-list-hero id="list" manual>
      <template is="dom-repeat" items="[[records]]" as="item">
     <simple-card hero-id$="[[index]]" first$="[[item.First]]" last$="[[item.Last]]"></simple-card>
      </template>
 </zero-list-hero>

[zerodevx]

definitely need more info than that - could you paste your full code - or better still do a repro in jsbin.