Paint 4.1.0 accidentally dies under OS X 10.9.5

I tried to set up an Nginx + Varnish + Apache configuration. Nginx is a proxy for the SSL connection and everything works fine until the paint suddenly dies accidentally.

I was trying to search the internet but could not find anything that could solve my problem.

Here is the status:

lsof -i TCP: 80
COMMAND PID USER FD TYPE DEVICE SIZE / OFF NODE NAME
varnishd 6794 root 5u IPv4 0x9ace38e8114f07c3 0t0 TCP *: http (CLOSED)
varnishd 6794 root 6u IPv6 0x9ace38e7f8c798fb 0t0 TCP *: http (CLOSED)

My server info:

Software:
System version: OS X 10.9.5
Kernel version: Darwin 13.4.0

Paint 4.1.0
Apache 2.4.33
nginx 1.15.1

Hardware:
Model ID: Xserve3,1
Processor name: quad-core Intel Xeon
Processor speed: 2.93 GHz

Memory: 48 GB