Unsure, but I uploaded the mod to my multiplayer server, and seems when someone joins they get an event handler / not multiplayer (save/load) safe.

I have done no multiplayer testing yet, I will try to do some later today or tomorrow

I was very pleased when I saw that someone was offering an alternative mod, but unfortunately, now we have exactly the same problem.
Multiplayer support would be really nice :)

I finally did some multiplayer testing today, and everything just worked perfectly for me without doing any code changes, tested both hosting as well as joining my friends when they host. Can you guys give me additional context? are you using dedicated servers or in game hosting? was there any additional info in any error messages?

It seems to happen after they're placed/configured, filled with items, and another player who wasn't there at the time joins.

170.430 Error ClientMultiplayerManager.cpp:1080: mod-train-loader was registered for the following events when the map was saved but has not re-registered them as a result of loading: on_gui_checked_state_changed (ID 3)
170.430 Error ClientMultiplayerManager.cpp:85: MultiplayerManager failed: "" + multiplayer.script-event-mismatch + "
" + "
mod-train-loader"

We tried this in our dedicated server and got the error. here is how we surmised it happens.

It seems to trigger for anyone that joins the server after the loader is placed. Looks like some sort of failure to sync the map state with the new player.

in game error: https://pasteboard.co/949SlR0heYoQ.png

log:
170.430 Error ClientMultiplayerManager.cpp:1080: mod-train-loader was registered for the following events when the map was saved but has not re-registered them as a result of loading: on_gui_checked_state_changed (ID 3)
170.430 Error ClientMultiplayerManager.cpp:85: MultiplayerManager failed: "" + multiplayer.script-event-mismatch + "
" + "
mod-train-loader"

Ok I think I actually fixed it. just uploaded a new version that was actually working for me, even after I managed to recreate the exact errors megaoka and Hinoken had.