Xenserver live migration requires VM reboot - heterogeneous Nodes

We want to migrate multiple VM hosted on XenServer 7.1 to XenServer 7.6. Live migration works but the VM on the source server is in hung state, Only option we have is to reboot the VM after life migration completes. I have see multiple posts regarding the Live migration, it was suggested to use command line but could not get the exact command working as in pool we have not assigned the default storage to be use. Below error received while executing the xe-mitra 
"You gave an invalid object reference. The object may have recently been deleted. The class parameter gives the type of reference given, and the handle parameter echoes the bad value given.
class: SR" 

xe vm-migrate remote-master=hostip remote-username=<username> remote-password="host password"  vm="VM Name" host-uuid=host UUID --live

Can this be checked on highest priority, we need to live migrate VM off the host a