Hi @liorg2,
The fact that this only happens sometimes makes me wonder if there's several Kibana versions behind your load balancer, depending on the Kibana server you reach, the bundle might or might not be available.
Can you please reach out to Elastic Cloud support with your deployment ID? You can use the contact form from cloud.elastic.co or email support@elastic.co. That way we'd be able to provide more detailed support to your specific deployment.