`--sequence` for multisig

[mr-t | Ark Protocol]

Someone can explain me how multisig signing and broadcast works? I did it multiple times, but sometimes it gets completely stuck, even adjusting gas limits it doesn't help.
I wonder what sequence in signed tx is? Like:

{
  "signatures": [
    {
      "public_key": { "@type": "/cosmos.crypto.secp256k1.PubKey", "key": "..." },
      "data": { "single": { "mode": "SIGN_MODE_LEGACY_AMINO_JSON", "signature": "...." } },
      "sequence": "6"
    }
  ]
}

So here it is sequence 6, if I create another offline tx and sign it, it gets sequence 7. When broadcasting it, it just hangs. So if sequence is the reason. How do I delete an older sequence?

@DariuszDepta