Hypershift Operator pods are running with higher PriorityClass but external-dns is set to default class with lower preemption priority, this has made the pod to preempt during migration. 
Observed while performance testing dynamic serving spec migration on MC.

# oc get pods -n hypershift 
NAME                           READY   STATUS    RESTARTS   AGE
external-dns-7f95b5cdc-9hnjs   0/1     Pending   0          23m
operator-956bdb486-djjvb       1/1     Running   0          116m
operator-956bdb486-ppgzt       1/1     Running   0          115m

external-dns pod.spec
  preemptionPolicy: PreemptLowerPriority
  priority: 0
  priorityClassName: default

operator pods.spec
  preemptionPolicy: PreemptLowerPriority
  priority: 100003000
  priorityClassName: hypershift-operator


    

On Management Cluster 4.14.7
    

Always

    1. Setup a MC with request serving and autoscaling machinesets
    2. Load up the MC to its max capacity
    3. Watch external-dns pod gets preempted when resources needed by other pods
    

External-dns pod goes to pending state until new node comes up
    

Since this is also a critical pod like hypershift operator, as it would affect HC dns configuration, this one needs to be a higher priority pod as well.
    

stage: perf3 sector