Why does adding a third productVariant trigger an ECONNRESET error?

[dugiwarc]

The query below works perfectly fine with an estimated cost of 702, but an actual of 59 that I send to the graphql.json endpoint. 
However if I add a third productVariant, I get an ECONNRESET error, where the cost is also 702 which is very well below the limit. 

Why is that ? 

query GetProductVariants($productVariantId0: ID!, $productVariantId1: ID!) {
    
      PRODUCT_0: productVariant(id: $productVariantId0) {
        ...ProductVariantFields
      }
  
      PRODUCT_1: productVariant(id: $productVariantId1) {
        ...ProductVariantFields
      }
  
  }

    fragment ProductVariantFields on ProductVariant {
      price
      sku
      id
      inventoryQuantity
      inventoryManagement
      inventoryPolicy
      inventoryItem {
        id
        inventoryLevels(first: 1) {
          edges {
            node {
              location {
                id
              }
            }
          }
        }
      }
    }