Data Action JSON mapping ignores nested fields

Built a Data Action to hit our internal CRM endpoint. The response comes back clean, but Architect won’t map the nested customer.tier field to the variable.

{
 "customer": {
 "id": 123,
 "tier": "gold"
 }
}

Tried response.customer.tier and response["customer"]["tier"] in the mapping config. Both fail silently. Is the parser broken for objects?