Cannot join. The following mod event handlers are not identical between you and the server. This indicates that the following mods are not multiplayer (save/load) safe. (See the log file for more details):

mod-rubber-ducky

252.746 Error ClientMultiplayerManager.cpp:1074: mod-rubber-ducky was registered for the following events when the map was saved but has not re-registered them as a result of loading: on_entity_died (ID 4), on_built_entity (ID 6), on_pre_player_mined_item (ID 11), on_robot_built_entity (ID 14), on_robot_pre_mined (ID 15), script_raised_built (ID 79), script_raised_destroy (ID 80), script_raised_revive (ID 81) and on_entity_spawned (ID 136) 252.746 Error ClientMultiplayerManager.cpp:99: MultiplayerManager failed: "" + multiplayer.script-event-mismatch + " " + " mod-rubber-ducky" 252.746 Info ClientMultiplayerManager.cpp:610: UpdateTick(50753363) changing state from(ConnectedLoadingMap) to(Failed)

If you comment out these lines at the bottom of control.lua does it work?
(so you are taking the rw_entity stuff outside of the on_configuration_changed)

--script.on_configuration_changed(function()
rw_entity.track({name = "rubber-ducky-factory"})
rw_entity.init()
--end)

Yes!*

*As long as I manually install the modified mod on my client.

I'll integrate that fix in the next version and let you know when it's in place.

I think this is properly fixed in the latest version, but I don't play multiplayer, so can you let me know if you are still having issues?