z_sendmany "Invalid state" with code=-25 #82

I attempted to send a ztx via z_sendmany to a single zaddr, and this is reported by z_getoperationstatus

"id": "opid-dc96d826-72c0-4c28-bad4-c9eeda1823c4",
    "status": "failed",
    "creation_time": 1638366600,
    "error": {
      "code": -25,
      "message": "Invalid state: "
    },
    "method": "z_sendmany",

From debug.log:

2021-12-01 13:52:56 ShuffleOutputs: Shuffling 8 zouts
2021-12-01 13:53:00 Build: Created spendAuth and binding sigs
2021-12-01 13:53:06 sendrawtransaction: Submitting to mempool
2021-12-01 13:53:06 opid-dc96d826-72c0-4c28-bad4-c9eeda1823c4: z_sendmany finished (status=failed, error=Invalid state: )

SilentDragon does not show this data anywhere in it's UI, which is extra confusing for GUI users.

dupe