SSHLauncher{host='myhost', port=22, credentialsId='aaa-bbb-ccc-myRealCredentials', jvmOptions='', javaPath='/home/bla/jenkins/bin/java', prefixStartSlaveCmd='', suffixStartSlaveCmd='', launchTimeoutSeconds=210, maxNumRetries=10, retryWaitTime=15, sshHostKeyVerificationStrategy=hudson.plugins.sshslaves.verifiers.ManuallyTrustedKeyVerificationStrategy, tcpNoDelay=true, trackCredentials=true}
[02/04/19 22:09:16] [SSH] Opening SSH connection to ligenr10.swb.siemens.de:22.
[02/04/19 22:09:16] [SSH] SSH host key matches key seen previously for this host. Connection will be allowed.
[02/04/19 22:09:16] [SSH] Authentication failed.

Manage old data complained on startup - ( didn't take real notice of message )

Credentials, private key, was corrupted when starting Jenkins after updating to 2.163

Eventually found and resolved.

( Jenkins- Credentials->System->Global Credentials -> name )

( updated Private Key - entered directly )

Might not be a bug but user error. However, caused 8 hour loss of Jenkins until problem found.