Gaming connection issues

Thank you for the reply.  Listed below are the answers to the questions you asked.   I would also like to make it known that I am more than 100% sure it's not the Netgear issue.  My reason for posting was because Comcast and the game companies are not providing any help what so ever.   So I figured I would ask networking people to see if they can shed some light on this. :)

1. Is the modem provided by Comcast a modem-only device or a combination of modem-router?

• The comcast modem is also the gateway which does routing

1. Is it possible to connect all or some of the gaming PCs, Xbox One, Xbox 360, and PS4 directly to the modem? If yes, are you able to play online just fine?

• .. same issue.  If i plug directly into the 5 ports available on the Comcast modem, its the same issue

1. Is the GS748Tv4 being used as a pass-through switch?

• Yes, I turned off all switching and made is as much like a HUB as I possibly could.

1. Is the network setup at your home network the same as with the gaming cafe shop? You may post screenshots of the detailed network setups.

• Home and work are different, but the concept is still the same.  The Comcast mode for home is differnt than the business calls mode.  At home, I do not have any additional routing or switch involved.  I just use the 5 ports on the modem itself.  As for the business class mode, I go from the wall to the modem then to the Netgear GS748, which then feeds all the machines.  

1. What is the current firmware version of the GS748Tv4?

• FW version 5.4.2.18

The Netgear switch is working great and I'm not having issues with the majority of the games.  It seems like certain games (mainly EA games and the new Halo 5) are doing some kind of IP check and if it see's more than two devices with the same IP, it kicks the machines off.   This would be so much easier if I could get the gaming companies to reply, but have a cut and paste response that it's my NAT settings or something else.   I'm not ruling out NATing issues, but right now, I got most machines showing up as "Open".   If any of the systems are set to "Strict" then it wont connect for sure. 

I hope this helps a little.  I'm really expecting a miracle at this point. :)