snoodler
Many thanks for your report.
This is not an error you see but the raw PHP file which is not parsed obviously. Hence the PHP handler is down. You use Lighttpd as webserver, I guess?
Please run the following and paste output:
journalctl -u php7.3-fpm
systemctl restart php7.3-fpm
cat /var/log/php7.3-fpm.log*