Unknown Exception Error when Using doubleFirst in postagg

I’m trying to write a postagg metric that returns the following:

(A / (B + C) ) * 100 — it’s a percent

Where A is a simple filtered aggregation, B is a simple filtered aggregation, and C is a simple doubleFirst aggregation. Currently I have A, B, and C built as their own metrics in Superset (types filtered, filtered, and doubleFirst, respectively).

A, B, and C return the expected values.

I’m able to get my postagg metric to work when I don’t include C. However, when I include C, I get an unknown exception error. Here’s the code for C:

{
  "type" : "doubleFirst",
  "name" : "beginning_soh",
  "fieldName" : "stockOnHand"
}

Here’s the code for my postagg. I’ve also tried listing the code for C (just above) directly in here, instead of using finalizingFieldAccess (I’ve also tried using just fieldAccess):

{
  "type"  : "arithmetic",
  "name"  : "closed_vial_wastage_rate",
  "fn"    : "*",
  "fields": [
    {
      "type" : "arithmetic",
      "name" : "closed_vial_wastage_rate",
      "fn" : "/",
      "fields": [
        {
          "type": "fieldAccess",
          "name": "closed_vial_wastage",
          "fieldName": "closed_vial_wastage"
        },
        {
          "type" : "arithmetic",
          "name": "managed_stock",
          "fn": "+",
          "fields": [
            {
              "type": "fieldAccess",
              "name" : "managed_stock_receipts",
              "fieldName" : "managed_stock_receipts"
            },
            {
              "type": "finalizingFieldAccess",
              "name": "beginning_soh",
              "fieldName": "beginning_soh"
            }
          ]
        }
      ]
    },
    {
      "type"  : "constant",
      "name"  : "cvw_percentage",
      "value" : 100
    }
  ]
}

Hello,

Im also experiencing this issue for metrics doubleFirst and doubleLast. By any chance, were you able to fix this?