Blockscout: "Unknown Action" when getting account balance for a specific address (ETH Mainnet)

[pedrouid]

I'm using blockscout.com API and I'm getting very similar issue to #1346 but I have it for a different address and network.

Whenever I try to get the account balance for 0x6e4d387c925a647844623762ab3c4a5b3acd9540 on ETH Mainnet using the following request.

GET https://blockscout.com/eth/mainnet/api?module=account&action=balance&address=0x6e4d387c925a647844623762ab3c4a5b3acd9540

I get the Unknown Action error response

{
    "status": "0",
    "result": null,
    "message": "Unknown action"
}

However I don't get this issue with other addresses as for example: 0xcBec15583A21C3ddAD5fab658be5b4FE85Df730b

[vbaranov]

Just for the record: from my tests, this issue can spontaneously appear/disappear for any address on every chain.

[pedrouid]

Could we get a different error message for what's causing this issue?

[vbaranov]

We will figure out what is the root cause and will try to eliminate this.

[FuZuK]

I think this is due to the fact that fetched_coin_balance for this address is null in the addresses table.