My friend hosted a server with these same set of mods we used a couple years back... Basically, the game would crash if an electric pole is placed that connects to more than two other power lines. All players except for the host will crash if anyone is to do this.

66.366 Info ClientMultiplayerManager.cpp:607: UpdateTick(2062807) changing state from(ConnectedLoadingMap) to(TryingToCatchUp)
66.983 Info ClientMultiplayerManager.cpp:607: UpdateTick(2063209) changing state from(TryingToCatchUp) to(WaitingForCommandToStartSendingTickClosures)
67.114 Info ClientMultiplayerManager.cpp:607: UpdateTick(2063209) changing state from(WaitingForCommandToStartSendingTickClosures) to(InGame)
67.214 Info GameActionHandler.cpp:4322: UpdateTick (2063215) processed PlayerJoinGame peerID(1) playerIndex(2) mode(connect)
75.180 Info ClientSynchronizer.cpp:319: Latency changed to (14)
80.181 Info ClientSynchronizer.cpp:319: Latency changed to (12)
85.181 Info ClientSynchronizer.cpp:319: Latency changed to (11)
110.181 Info ClientSynchronizer.cpp:319: Latency changed to (8)
117.814 Script @HelicopterRevival/control.lua:134: control.heliBuilt
127.064 Script @HelicopterRevival/control.lua:134: control.heliBuilt
128.198 Script @HelicopterRevival/control.lua:134: control.heliBuilt
132.131 Script @HelicopterRevival/control.lua:134: control.heliBuilt
133.497 Script @HelicopterRevival/control.lua:134: control.heliBuilt
135.480 Script @HelicopterRevival/control.lua:134: control.heliBuilt
137.964 Script @HelicopterRevival/control.lua:134: control.heliBuilt
142.315 Script @HelicopterRevival/control.lua:134: control.heliBuilt
153.197 Script @HelicopterRevival/control.lua:134: control.heliBuilt
154.797 Script @HelicopterRevival/control.lua:134: control.heliBuilt
157.915 Script @HelicopterRevival/control.lua:134: control.heliBuilt
158.997 Script @HelicopterRevival/control.lua:134: control.heliBuilt
160.165 Info ClientSynchronizer.cpp:319: Latency changed to (7)

I get this for 600 lines until...

634.047 Script @HelicopterRevival/control.lua:134: control.heliBuilt
634.880 Script @HelicopterRevival/control.lua:134: control.heliBuilt
635.714 Script @HelicopterRevival/control.lua:134: control.heliBuilt
640.664 Script @HelicopterRevival/control.lua:134: control.heliBuilt
644.080 Script @HelicopterRevival/control.lua:134: control.heliBuilt
647.598 Script @HelicopterRevival/control.lua:134: control.heliBuilt
650.365 Info ClientSynchronizer.cpp:319: Latency changed to (13)
651.865 Script @HelicopterRevival/control.lua:156: control.heliDestroyed
661.765 Script @HelicopterRevival/control.lua:134: control.heliBuilt
661.797 Error GameActionHandler.cpp:2686: Multiplayer desynchronisation: crc test (heuristic) failed for crcTick(2098885) serverCRC(4053903891) localCRC(908680430)
661.797 Info ClientMultiplayerManager.cpp:607: UpdateTick(2098886) changing state from(InGame) to(DesyncedWaitingForMap)
661.930 Info ClientMultiplayerManager.cpp:740: updateTick(2098887) received player (1) desynced
662.580 Info ClientMultiplayerManager.cpp:746: Received mapReadyForDownload
662.580 Info ClientMultiplayerManager.cpp:607: UpdateTick(2098887) changing state from(DesyncedWaitingForMap) to(DesyncedCatchingUpWithMapReadyForDownload)
662.580 Error GameActionHandler.cpp:2686: Multiplayer desynchronisation: crc test (heuristic) failed for crcTick(2098886) serverCRC(3228584404) localCRC(256775577)
662.598 Error GameActionHandler.cpp:2686: Multiplayer desynchronisation: crc test (heuristic) failed for crcTick(2098887) serverCRC(1020113504) localCRC(1137036617)

Is there a reason for the desync? We haven't made a single helicopter yet and would love to keep using this mod. (Sorry for the blast of info)

From the log, doesn't look like HR was the culprit...
See this?

Info ClientSynchronizer.cpp:319: Latency changed to (13)

to this:

661.797 Error GameActionHandler.cpp:2686: Multiplayer desynchronisation: crc test (heuristic) failed for crcTick(2098885) serverCRC(4053903891) localCRC(908680430)
661.797 Info ClientMultiplayerManager.cpp:607: UpdateTick(2098886) changing state from(InGame) to(DesyncedWaitingForMap)
661.930 Info ClientMultiplayerManager.cpp:740: updateTick(2098887) received player (1) desynced
662.580 Info ClientMultiplayerManager.cpp:746: Received mapReadyForDownload

Seems like network just gave up on map retrieval...

Yes, unfortunately I'm well aware of the spam that my mod is causing; there had been quite a few complaints about it, and it'll be cleaned up, but it really isn't the cause for map desync... Unless this happens regularly and the only mod is heli... Is it? Because I hadn't gotten any other report about it...