Maybe use python with https://github.com/ethereum/py_ecc to implement ECRECOVER, make sure its results are solidity-compatible, but watch each step of the ecrecover procedure and see where it starts “not going according to plan”?
Maybe use python with https://github.com/ethereum/py_ecc to implement ECRECOVER, make sure its results are solidity-compatible, but watch each step of the ecrecover procedure and see where it starts “not going according to plan”?