ThingsBoard Website Unavailability (503 Service Unavailable)

Hello.

Have you checked the system log when an error occurs in EC2?
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/troubleshoot-unreachable-instance.html#instance-console-console-output

Also, what was the CPU usage rate and memory usage rate of EC2 when the error occurred?
If there is a problem with the specs of the instance type, try selecting a larger instance type.

How I can select larger instance without loosing the instance data