Upgrade of plugin google-compute-engine-plugin to version 1.0.10 causes that vm instances created in this same GCP project but from different Jenkins Master are removed.
It looks that these changes https://github.com/jenkinsci/google-compute-engine-plugin/blob/7ee660eae173d1010388c557c378f2b7f8bdd105/src/main/java/com/google/jenkins/plugins/computeengine/CleanLostNodesWork.java#L66 trying to cleanup all nodes with this same instanceUniqueId which is resolved only from cloud name. I think it is quite possible that for simplicity cloud name in most cases is identical with project id.
So detection of unique instances should probably ensure that vm instances comes from this same jenkins master before they are deleted.
As workaround different cloud names could be used on each jenkins master.