I think it's possible, that this is also dependent to Rampant, so I post this also here.

I did build some landfill over small lakes. I didn't look deeper into it, but maybe it's a Bug with pathfinding?! I'll post this bug also in Construction Drones mod....

The mod Construction Drones (0.5.5) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Construction_Drones::on_script_path_request_finished (ID 112)
The mod Rampant (0.18.11) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Rampant::on_robot_built_tile (ID 47)
Rampant/control.lua:783: attempt to index field 'item' (a nil value)
stack traceback:
Rampant/control.lua:783: in function <Rampant/control.lua:779>
stack traceback:
Construction_Drones/script/construction_drone.lua:2180: in function <Construction_Drones/script/construction_drone.lua:2125>
(...tail calls...)
Construction_Drones/script/construction_drone.lua:2680: in function 'handler'
core/lualib/event_handler.lua:47: in function <core/lualib/event_handler.lua:45>
stack traceback:
[C]: in function 'raise_event'
Construction_Drones/script/construction_drone.lua:2180: in function <Construction_Drones/script/construction_drone.lua:2125>
(...tail calls...)
Construction_Drones/script/construction_drone.lua:2680: in function 'handler'
core/lualib/event_handler.lua:47: in function <core/lualib/event_handler.lua:45>

I guess it's Rampant, because the error happened after update.
When I deactivate Rampant everything works again.
I can reproduce it every time. If you need the save, please tell me.

same here, except i got the error with road grid and rampant:

The mod Road Grid (0.0.3) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event road-grid::on_chunk_generated (ID 12)
The mod Rampant (0.18.11) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Rampant::on_robot_built_tile (ID 47)
Rampant/control.lua:783: attempt to index field 'item' (a nil value)
stack traceback:
Rampant/control.lua:783: in function <Rampant/control.lua:779>
stack traceback:
road-grid/control.lua:26: in function <road-grid/control.lua:16>
stack traceback:
[C]: in function 'raise_event'
road-grid/control.lua:26: in function <road-grid/control.lua:16>

This is the event in question
https://lua-api.factorio.com/0.18.24/events.html#on_robot_built_tile

It doesn't have optional next to the item or the stack.

This is the place construction bots raises the event.
https://github.com/Klonan/Construction_Drones/blob/master/script/construction_drone.lua#L2180

The event data is here https://github.com/Klonan/Construction_Drones/blob/master/script/construction_drone.lua#L2166

Notice that it doesn't have all the required parameters.

Road grid does the same thing.

I will have to come up with a new mechanism for detecting when landfill or waterfill are used.

this should be fixed in the latest