SSH is being blocked when I install containerized Frappe on AWS EC2

I have been trying to get Frappe to work on an AWS EC2 instance, using Docker.

At some point in the installation—I’m not sure exactly when—it appears that the SSH port (port 22) is being blocked. I burned through quite a number of EC2 instances before I realized what was happening.

I have worked around this by changing the SSH port to something other than 22 before I precede with installation.

But I wonder if this behavior is documented somewhere, or if there is a reason the port is being disabled.

Thanks

docker setup is not doing anything with port 22.