HAD unregistration problem with gab (failed) : VCS 6.0

Dear Team,

I'm a newbi here. 

We have a VCS setup on two linux (6.4) nodes (SFCFSHA 6.0). When customer tried to reboot a master node, the following error messages (confirming that HAD has unregistered with VCS (retry 1) FAILED) appeared on iLOM and it caused the panic on slave node too. Now the node is up and everything looks okay. But we have to find out the cause for this error message.

Please check the attached file for screenshot of the error message.

Looking forward for your help.

Thanks and Regards

Barani