LAN Multiplayer constant lag spikes/dropping only computer-computer

[A_Deer]

I have a older I5-3470 computer and a newer Ryzen 5 3600 computer.

Both computers can run massive complex factories without any issues when in single player. Both computers are rock steady at FPS/UPS = 60/60 when in single player

LAN multiplayer is currently not possible no matter which computer hosts the game. Connecting to a new game with no tech the connecting client freezes every 5 to 10 seconds and gets "server is not responding" and the host always sees "<username> dropping". It will recover after about 3 seconds and catch back up, it wont actually drop anyone from the server. I hosted on the slow computer, and hosted on the fast computer, no difference.

This is a LAN game mind you, no internet. Ping when connected computer to computer shows 254 rock steady in the game.

I have tried slowing the game speed down to .5 and that made no change. The client will still freeze and show "server not responding"

After the "server is not responding" goes away the connected client will see a spike in UPS up to about 150 I presume to catch up with the server. this is identical weather its the slow or faster computer connecting.

All clients are connected to my access point via wireless connection. I have tested all computers several times, pings show 0ms and zero packet loss to the router.

I have attached the log file as well as some screen shots of what happens.

[A_Deer]

And I just solved my own problem. . . . I don't know why though.

All the connections tested good outside of the game. The older I5 computer is using a USB network card.

I moved the USB network card from the front USB 3.0 port, to a rear USB 3.0 port.

Making that change solved the issue. My ping dropped from 254, down to 8. And its rock steady and no more lag issues.

There must be some issues with the front USB ports on that system.

I started a headless server on a different system and it worked perfectly fine. Thats what pointed me to the I5 system being an issue. The headless server has the same exact network card in the same front port with no issues.