Why Won't OpenShift Pods Schedule? (PodFitsHostPorts, CheckServiceAffinity, MatchNodeSelector, Insufficient memory etc)

Issue

• I keep seeing this error in the pods events:

0:41 PM Warning Failed scheduling   pod (router-4-7364e) failed to 
fit in any node fit failure on node (10.193.188.224): PodFitsHostPorts
fit failure on node (10.193.188.91): PodFitsHostPorts
fit failure on node (10.193.188.15): CheckServiceAffinity
fit failure on node (10.193.188.74): CheckServiceAffinity
fit failure on node (10.193.188.82): OutOfDisk

• Pods will not schedule
• Trying to deploy pods and it errors with: "failed to fit in any node fit failure summary on nodes: CheckServiceAffinity (9), MatchNodeSelector (9), InsufficientMemory (2)"
• Trying to deploy router, registry, or another application in OpenShift
• Fails to run properly with:

"Error scheduling default router-1-deploy: pod (router-1-deploy) failed to fit in any node"

• Also see:

# oc get pods
NAME              READY     STATUS              RESTARTS   AGE
router-1-deploy   0/1       ContainerCreating   0          45m

# oc logs router-1-deploy
Error from server: container "deployment" in pod "router-1-deploy" is waiting to start: ContainerCreating