hello apa,
we’ve tested locally to confirm disk encryption is working (JP-5.1.2/r35.4.1). you may see-also forum topic, Topic 264454 for the test steps.
please double check you’re using [Driver Package (BSP) Sources] package with identical L4T release version if you’re using a customize key for disk encryption. you may see-also Topic 271974 for the magic bytes to examine your EKS image.