Slider 0.92 on CDH 5.5.1 (Hadoop 2.6) - AM log shows NPE at component heardbeat URI

Hi Running slider 0.92 on CDH 5.5.1 (which is Hadoop 2.6), with Kerberos I am deploying a application with multiple components. The components start but fail to heart beat to slider AM. The slider AM log shows NPE at container heartbeat URLs as below. I have attached the complete slider AM log

slider AM not restarting app

I had a slider job where the AM was running, and the application had failed, but the AM wasn't trying to restart the app, but it didn't fail the job, or even start a new attempt. If just sat there doing nothing. I haven't looked at the default slider appmaster closely so I don't understand