Nginx Marks Site Unavailable

Have version 1.17.2 (free version)
Have it setup as a load balancer with 2 machines behind it. Periodically the Nginx Marks both servers unavailable and get back a 504 message. The 2 servers are just front end servers running Apache that forwards request to other servers.
Can do a crtl R (constant refresh holding it down), no problem, pause and start doing a crtl r manually and we can see the page just spinning.
TCPDUMP shows request going to servers (firewall packet sniffer), on the...

Nginx Marks Site Unavailable

from Nginx https://ift.tt/2Urifln
via IFTTT