The Buy Bales mod, it spawns a fake vehicle that does not define any lights.
All standard vehicles defines lights, but this one does not.
It seems like the "Realistic beacons" mod is dependent on the vehicle type to use the specialization "<specialization name="lights" />" or you will get this error I posted in my previous message.
1 Comments for Realistic beacons
If a vehicle does not define any beacons, this error occurs:
Error: Running LUA method 'update'. C:/Users/Markus/Documents/My Games/FarmingSimulator2017/mods/FS17_RealisticBeaconLights/VariableBeaconLights.lua:18: bad argument #1 to 'pairs' (table expected, got nil)