Crashing when trains present

[Winston]

I searched a bunch for this issue and friend and I are having and it appears to be the same bug from 2 years ago that causes client crashes in multiplayer when the train missions are active or there's a lot of train activity. Something about excessive lag or de-sync.
I have a dedicated server on a different PC on my network so I'm able to reconnect, but he is not from over the internet, it keeps timing out.

I was able to complete the mission and then pull up the track then he could join again.

[Winston]

Ok, it's actually worse than I thought. I don't think it's trains or the amount of items in the world specifically. The connection times out when trying to connect as it appears to be transferring the save file to the player. It seems to have a default transfer speed that is really low, so large save files take a long time, either triggering a built in timeout setting or just failing. There is a method to increase the transfer rates (used to fix lag in Satisfactory) which isn't too difficult to apply that greatly increases the join speed and fixed the issue.

Unfortunately in my troubleshooting, I enabled creative mode to quickly delete items from our save. Without realising this has disabled all mission progress, so the game is basically over. The prompt that warns about this did not appear until I went to disable creative mode.

Disappointing all round, we'll probably refund the DLC as there's no missions for it now and the whole experience left a bad taste.