I'm running Ubuntu 20.04.3 on a 1 GB RAM 1 VCPU 40GB SSD Lightsail instance. It runs NGINX serving a single Wordpress instance. The WP site is the web presence of our local Apple user group and gets very little traffic.
About once a month (plus or minus a few days) the Wordpress site goes away.
When that happens I'm unable to SSH into the Lightsail instance, neither through my SSH client (iTerm2) nor the AWS console. It appears to connect, but the screen is blank and there is no login prompt.
Rebooting the instance from the AWS console has no effect on the issue.
If I stop and restart the Lightsail instance everything comes back, but the public IP address has changed which means I need to make changes to DNS.
Syslog doesn't show anything I can see as the problem.
Any suggestions as to what I should be looking for?