Client FPS/UPS drops until unplayable

On a LAN game the host can play the game just fine at ~60 FPS/UPS, but the client drops down to 5 FPS/UPS where he becomes completely paralyzed and cannot move. The game is literally unplayable.

I've attached images of some debug info, can anyone help me understand the numbers? I've also attached the map so you can see it's not a gigafactory. The PC can play a bunch of nice looking 3D games, and even horribly optimised CPU-dependent games like Civ:V, but it rolls over and dies even when I stand in the middle of nowhere, zoomed into the dirt with smoke turned off.

Factorio 0.14.20
Win10 64
AMD FX-4100 CPU @ 4.4GHz (using about 30%)
4GB DDR3 (using about 50-60%)
HDD
AMD Radeon 4670 (34% load, 328MB memory usage)

No supercompter, but I can't believe it's literally unable to draw a few sprites a few times a second! It works okay in singleplayer, 50-55 FPS in singleplayer, but locks up in multiplayer.

Statistics: Posted by Llama — Mon Nov 28, 2016 2:36 am