Parity-ethereum: Parity PoA with Aura takes 120 seconds between blocks even with "stepDuration": "5"

[phoax]

I'm running:

• Parity version: 1.8.2-beta
• Operating system: Linux
• And installed: via installer

actual
I have followed the Demo-PoA-tutorial, with a smart contract to deal with authorities. It works fine except the mining delay between two blocks is too long. It takes 120 seconds.

My spec.json is:

{
  "name": "PrivatePoA",
  "engine": {
    "authorityRound": {
      "params": {
        "blockReward": "0x4563918244F40000",
        "stepDuration": "5",
        "validators" : {
          "safeContract": "0x0000000000000000000000000000000000000005"
        }
      }
    }
  },
  "params": {
    "gasLimitBoundDivisor": "0x400",
    "maximumExtraDataSize": "0x20",
    "minGasLimit": "0x1388",
    "networkID" : "0x2323"
  },
  "genesis": {
    "seal": {
      "authorityRound": {
        "step": "0x0",
        "signature": "0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
      }
    },
    "difficulty": "0x20000",
    "gasLimit": "0x5B8D80"
  },
  "accounts": {
    "0x0000000000000000000000000000000000000001": { "balance": "1", "builtin": { "name":   "ecrecover", "pricing": { "linear": { "base": 3000, "word": 0 } } } },
    "0x0000000000000000000000000000000000000002": { "balance": "1", "builtin": { "name": "sha256", "pricing": { "linear": { "base": 60, "word": 12 } } } },
    "0x0000000000000000000000000000000000000003": { "balance": "1", "builtin": { "name": "ripemd160", "pricing": { "linear": { "base": 600, "word": 120 } } } },
    "0x0000000000000000000000000000000000000004": { "balance": "1", "builtin": { "name": "identity", "pricing": { "linear": { "base": 15, "word": 3 } } } },
    "0x0000000000000000000000000000000000000005": { "balance": "1", "constructor" : "0xbytecode..." }
  }
}

expected behavior
How to reduce mining time between block to a few seconds?

[keorn]

By default Aura will produce empty blocks only once in a while. To have it produce a block on every step use --force-sealing on the authority nodes.
You can also change:

  --reseal-max-period MS           Specify the maximum time since last block to enable
                                   force-sealing. MS is time measured in
                                   milliseconds (default: 120000).

[phoax]

Thanks a lot!