Network Error, nginx & ProcessWire 3.0.62

[RyanJ]

Hello!

Looking for a bit of advice or suggestions here. I don't claim to be a nginx expert, but I have PW version 3.0.62 powering an app running on a cloud server with nginx. Everything operates fine for the most part, but from time to time I am getting a network error message when trying to navigate in the admin or just a plain ole 500 error. Specifically when logging in initially and trying to view the page tree. A pop up window appears with the network error message (I will grab a screen shot next time I see it). Also when navigating through the admin I get random 500 errors. 

php 5.6.x
nginx
cloud hosting service

A couple of corresponding logs below.

Error log in pw admin:

Error: Cannot instantiate abstract class ProcessWire\ProcessPageListRender (line 331 of /xxx/xxx/xxx/wire/modules/Process/ProcessPageList/ProcessPageList.module)

Nginx Error log:

017/05/12 10:11:47 [error] 7305#0: *14305329 readv() failed (104: Connection reset by peer) while reading upstream, client: xx.xxx.xxx.xxx, server: theserver, request: "GET /login/page/ HTTP/1.1", upstream: "fastcgi://unix:/xxxxx/dev/.php-fpm.socket:", host: "thehost", referrer: "http://domain/login/setup/logs/view/errors/"

017/06/21 14:15:29 [error] 29093#0: *106631997 readv() failed (104: Connection reset by peer) while reading upstream, client: xx.xxx.xxx.xxx, server: server, request: "GET /login/page/edit/?id=1489 HTTP/1.1", upstream: "fastcgi://unix:/xxxxx/dev/.php-fpm.socket:", host: "thehost", referrer: "http://domain/login/page/"

Thanks for your time.