Using ecrecover is against best practice. Preferably use ECDSA.recover instead. EIP-2 still allows signature malleability for ecrecover(). Remove this possibility and make the signature unique. However it should be impossible to be a threat by now.
Volt.sol#L89
Take these implementations into consideration
https://github.com/OpenZeppelin/openzeppelin-contracts/blob/4a9cc8b4918ef3736229a5cc5a310bdc17bf759f/contracts/utils/cryptography/draft-EIP712.sol
https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/extensions/draft-ERC20Permit.sol
