push_lowest_slot cannot sign the new crds-value unless the id (pubkey) argument passed-in is the same pubkey as in ClusterInfo::keypair(), in which case the id argument is redundant: https://github.com/solana-labs/solana/blob/bb41cf346/gossip/src/cluster_info.rs#L824-L845 Additionally, the lookup is done with self.id(), but insert is done with the id argument, which is logically a bug.