Im adding a hook to work around this:
case "$HOOK_EVENT" in
create)
echolog no action for create
;;
destroy)
echolog waiting for instance to be terminated
while [ ! aws ec2 describe-instances --instance-ids $instanceid| grep -q terminated ]
do
echolog waiting for $instanceid to terminate
sleep 10
echolog retrying termination
echolog running aws ec2 terminate-instances --instance-ids $instanceid
aws ec2 terminate-instances --instance-ids $instanceid
done
echolog instance $instanceid now shows as terminated
;;
update)
echolog no action for update
;;
*)
echo "Usage: run_hooks {create|destroy|update}"
exit 1
;;
esac

Dominic Cleal wrote:

By simultaneously, do you mean using the tickboxes and select action dropdown, or with multiple tabs/windows?

I have been using api v2.