I think I’ve narrowed this down to the ec2-utils package. We had the same issue, related to devices not mounting properly that we initially thought was related to the ENA or NVMe driver. Once we ran a yum update, it was resolved.
If you downgrade the ec2-utils package to ec2-utils-1.2-2.amzn2 the issue returns. This seems to only affect nitro based instances. To fix it, you can temporarily boot as a t2 or other older instance type and update the package.
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