Observable game lag on a computer in same LAN larger than lag from internet

[Xilexio]

I start a DST dedicated server in online mode on a Windows 10, i5 @ 2x1.7GHz, 4GB machine in my LAN with appropriate ports forwarded on the router. Then I connect to it from a computer in my LAN, and a friend connects from outside. After a while, I observe much bigger lag than he does (I have around 5s observable lag, while he has <0.5s).

It doesn't seem to be connected to performance of my client machine, since graphics seem to run smoothly and the thing that's lagging is e.g. opening containers or picking things up. I noticed that my lag is much smaller in caves and it is temporarily better after restarting the server.

Is such a lag a known issue?

Is there a way to run a dedicated server both on LAN and online mode, in case the game gets the idea to send the data through the internet instead of keeping it in my LAN? How to deal with it?

[Littlecooldude]

are there any mods enabled? I get this lag when my wife and I have MiniMapHUD.

[Bracked]

I run a very similar setup to you except for my server is hosted on Debian 8. I use online mode and I haven't noticed the same issue. I don't think there is a way to do dual LAN/online modes.

One option would be to try just LAN mode and have the remote user connect to your network via VPN. I haven't tried this so I don't know if this configuration would work.

[Xilexio]

Thanks for the feedback.

@Littlecooldude: I do use mods, including Minimap HUD. However, the problem is that my friend also uses them and he observes only a normal network lag. But thanks for the idea, I'll try without this mod.

@Bracked: Do you use Minimap HUD and other mods too? Could it be that Linux version is better at it? I could try setting up the server on a VM to test it.