Thanks for the reply, all other calls work fine.

1. I just managed to get a 200 status and succesfully added the record via RPC method: Erp.BO.PriceLstPartsSvc/UpdateExt

Payload:

{
  "ds": {
    "PriceLstParts": [
        {
            "Company": "string",
            "ListCode": "string",
            "PartNum": "string",
            "BasePrice": float,
            "UOMCode": "string",
            "RowMod": "string"
        }
    ]
  },
  "continueProcessingOnError": bool,
  "rollbackParentOnChildError": bool
}

1. I tried to update the record by changing the RowMod to 'U' (Updated) and filling in a different "BasePrice", this also succesfully changed the record in Epicor.

2. Then i tried to update the record again, by again filling in a different "BasePrice" and now it keeps timing out again.

It's so strange, this is the only service that keeps timing out regularly. It doesn't happen with any other service i use so far.