Pods stuck in ContainerCreating with "failed to assign an IP address to container"
It seems that you reached maximum number of IP addresses in your subnet what can suggest such thing in documentation:
maxIPAddress: the maximum number of IP addresses that can be used for Pods in the cluster. (assumes there is enough IPs in the subnet).
Please take a look also on maxUnavailable and maxSurge parameters which controls how many PODs appear during rolling upgrade - maybe your configuration assumes that during rolling upgrade you will have over 600 PODs (like 130%) and that hit limits of your AWS network.