Indeed, which is why I've heard of failover setups where the backup has a means to make very sure that the main system is off before it takes over (often by cutting the power).
I did this systematically: at the first sign of outlier in performance one system would move itself to another platform and shut itself down. The shutdown meant turn all services off and let someone log in to investigate and rearrange it again. This system allowed different roles to be assigned to different platform. The platform was bare metal or bhyve vm. It worked perfect.