IMS - Network, is an Israeli gaming community that builds and develops game servers for free.  

What is a double net? 

Double NAT occurs when you connect your router to an ISP gateway or another router. Because NAT is performed by each router or gateway, your network is split into two different private networks.
The devices connected to one private network might have communication problems with the devices connected to the other private network.

As you can see in the illustration I have created an example for a double net issue.
The double net accounts between the routers, the main problem that you will experience will use port forwarding and triggering to not work.
which is a major problem... if you need to open a port... because you are running a server that players need to access. 

How to Identify a double net issue?

Look for 4 simple problems that can occur with a double net network:

• Online games
• VPN connections
• Port forwarding and triggering
• Secure websites that use SSL

How To Fix double net problems?

If your router is connected to an Internet service provider (ISP) gateway or another router, and you are having network problems, your network might be set up to perform double network address translation (NAT).

Note: If you connected another router to your ISP gateway or main router to improve WiFi coverage or add more LAN ports to your home network, you might want to consider other solutions.
If you have a particular area where you want to improve WiFi coverage, a WiFi extender is a better choice.
If you want to improve WiFi coverage throughout your entire home, a mesh WiFi system is ideal.
If you simply want to add more LAN ports to your existing router, an affordable unmanaged Ethernet switch is appropriate.

There are multiple ways to fix double NAT issues with your network.
Your options depend on whether your router.

Suggestion: Because all routers and ISP are different, I would recommend contacting your ISP and coordinating with their support team if you don't know what you are doing.

Most Common Way To Fix Double NET issues

If your router is connected to another router, you can resolve double NAT issues by removing the first router from your network, putting the first router in bridge mode,
or putting your router in access point (AP) mode.

I recommend that you remove the first router for the best network performance.
If you can’t remove the first router, check its capabilities to see if it supports bridge mode.
Most routers support bridge mode, but routers from other brands might not.
If you can’t remove or put the first router in bridge mode, you must put your main router in AP(access point) mode.

Note: Some router features are disabled in AP mode.

What Happened on IMS - Network's server infrastructure?

As all humans, we make mistakes that can cause problems or even break critical systems and operations... 
While Building an exception for our existing server room we used a router that was donated to us by a player on our server... 
After deploying the router nothing stood out of the ordinary
One day we had extra traffic of players on the server so our management application deployed extra Minecraft server instances.
Unfortunately, the ports failed to connect because we created a double net, which caused the existing server to overload with players and lag, and in our industry, you can't afford lags on your server.
We do have primitive figures and our team was immediately alerted but, the investigation into identifying the problem took us 2 weeks.