Hi, it seems to me like there is an isse in the interaction with staviq's nicefill:

The mod Construction Drones (0.4.9) 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 NiceFill (0.1.17) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event nicefill::on_robot_built_tile (ID 47)
__nicefill__/control.lua:312: attempt to index field 'robot' (a nil value)
stack traceback:
    __nicefill__/control.lua:312: in function <__nicefill__/control.lua:298>
stack traceback:
    __Construction_Drones__/script/construction_drone.lua:2102: in function <__Construction_Drones__/script/construction_drone.lua:2047>
    (...tail calls...)
    __Construction_Drones__/script/construction_drone.lua:2601: in function 'handler'
    __core__/lualib/event_handler.lua:44: in function <__core__/lualib/event_handler.lua:42>
stack traceback:
    [C]: in function 'raise_event'
    __Construction_Drones__/script/construction_drone.lua:2102: in function <__Construction_Drones__/script/construction_drone.lua:2047>
    (...tail calls...)
    __Construction_Drones__/script/construction_drone.lua:2601: in function 'handler'
    __core__/lualib/event_handler.lua:44: in function <__core__/lualib/event_handler.lua:42>

also posted in https://forums.factorio.com/viewtopic.php?f=190&t=57313&p=488974#p488974

let me know if you need logs or saves

Yea, nicefill just needs to check if the robot is nil