502 bad gateway issue has a separate topic. It appears to be related to something triggering the issue with pfBlocker's DNSBL. To be clear, the issue is still under investigation and I am not pointing fingers at pfBlockerNG. For now, disable DNSBL. Lastly, pfBlockerNG is not installed by default with pfSense as its a community developed package. We love and fully support pfBlockerNG development however it's not maintained by pfSense team.
https://forum.pfsense.org/index.php?topic=137103.255