Hi, log from a public serveer. Not quit sure what actually caused the problem.

3729.466 Info ServerMultiplayerManager.cpp:974: updateTick(11069332) received stateChanged peerID(7) oldState(TryingToCatchUp) newState(WaitingForCommandToStartSendingTickClosures)
3729.466 Info GameActionHandler.cpp:4318: UpdateTick (11069332) processed PlayerJoinGame peerID(7) playerIndex(7) mode(connect)
3731.100 Info ServerMultiplayerManager.cpp:974: updateTick(11069430) received stateChanged peerID(7) oldState(WaitingForCommandToStartSendingTickClosures) newState(InGame)
3786.183 Script @blueprint-sandboxes/scripts/illusion.lua:191: Replaced 0 entities in Sandbox Blueprint
3805.267 Error MainLoop.cpp:1432: Exception at tick 11073880: The mod Cybersyn Combinator (2.4.4) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event cybersyn-combinator::on_gui_click (ID 1)
LuaGuiElement API call when LuaGuiElement was invalid.
stack traceback:
[C]: in function 'newindex'
__cybersyn-combinator/scripts/gui.lua:628: in function 'handler'
flib/gui.lua:177: in function <flib/gui.lua:160>
3805.267 Error ServerMultiplayerManager.cpp:84: MultiplayerManager failed: "The mod Cybersyn Combinator (2.4.4) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event cybersyn-combinator::on_gui_click (ID 1)
LuaGuiElement API call when LuaGuiElement was invalid.
stack traceback:
[C]: in function 'newindex'
__cybersyn-combinator/scripts/gui.lua:628: in function 'handler'
flib/gui.lua:177: in function <flib/gui.lua:160>"
3805.267 Info ServerMultiplayerManager.cpp:806: updateTick(11073880) changing state from(InGame) to(Failed)
3805.283 Quitting: multiplayer error.
3805.283 Info GlobalContext.cpp:760: Deleting active scenario.
3805.835 Info ServerMultiplayerManager.cpp:146: Quitting multiplayer connection.
3805.835 Info ServerMultiplayerManager.cpp:806: updateTick(18446744073709551615) changing state from(Failed) to(Closed)
3805.835 Info ServerMultiplayerManager.cpp:166: Deleting active scenario (global = true).
3805.836 Info HttpSharedState.cpp:55: Downloading https://multiplayer.factorio.com/remove-game/19961662

Version: 2.4.4

One way I found to reproduce it is removing a section while editing one of the slots in it, is that what happened?

Sorry, I dont fully recall what happen at that time, but it sounds very like what you described here.

Version 2.4.5 is out now with a fix for that at least. Let me know if it happens again and if you can reproduce it with a save file!

Sure : )