Here is a solution that another community member is using to work around this (known) issue with the Alchemy provider:
Additionally, I experience a similar problem with different RPC providers when submitting raw transactions: the first call succeeds, but subsequent ones (from other nodes in the subnet) fail because the nonce has already been used.
Which RPC providers cause this to happen for eth_sendRawTransaction? This is also a known issue, and we are looking for ways to mitigate this.