The OpenEthereum client for Ethereum, formerly known as the Parity client, is reportedly malfunctioning for a number of users on Thursday afternoon UTC, including the popular block explorer Etherscan.
According to multiple user reports on GitHub, the OpenEthereum client has been stuck on block 12,244,294, or just 294 blocks after the Berlin hard fork was executed. The error message seems to indicate that the client is rejecting the new blocks, thinking that its state Merkle root is invalid.