Lightsail instance stops loading Wordpress site, requiring instance reboot

Wordpress website (bitnami package) running on Lightsail instance stops displaying after 2-3 days, requiring a restart. Bitnami offers a built-in diagnostic tool which states that ports 22, 80 and 443 are not accessible remotely at the time this issue persists. Lightsail instance networking/firewall settings show that the ports in question are enabled. Rebooting the Lightsail instance resolves the issue, but the problem repeats itself after 2-3 days. We have to keep restarting the server every couple days to keep the website live. Would like to find a reasonable solution.