INVALID_KEY

One of the keys used in this transaction is not valid.

[Error Code: 1008] error caused by: 1 error occurred: * transaction verification failed: [Error Code: 1006] invalid proposal key: public key 6 on account d8ffa2e4957295a0 does not have a valid signature: [Error Code: 1008] invalid payload signature: public key 0 on account 87ca73a41bb50ad5 does not have a valid signature: signature is not vali