Factorio 2.1.24 (build 87808), Eneas 1.0.10

Summary

The multiplayer server crashes with a non-recoverable error when a player
has researched friend-tech and the Eneas pollution check reaches the
medium level.

Error

Error while running event moon-eneas::on_nth_tick(60)
Unknown item name: Construction_Drone

stack traceback:
[C]: in function 'insert'
moon-eneas/prototypes/scripts/events.lua:825: in function 'deliver_supplies_to_lift'
moon-eneas/prototypes/scripts/events.lua:923: in function 'execute_pollution_check'
moon-eneas/prototypes/scripts/events.lua:1121: in function <events.lua:1100>

MultiplayerManager failed: "The mod moon-eneas (1.0.10) caused a non-recoverable error."
ServerMultiplayerManager.cpp:809: updateTick(...) changing state from(InGame) to(Failed)

Cause

SUPPLY_REWARDS.late_memory in prototypes/scripts/events.lua
(line 98-101) references Construction_Drone unconditionally:

late_memory = {
    tech_required = "friend-tech",
    items = {["Construction_Drone"] = {min = 1, max = 1}},
}

Construction_Drone is only provided by Construction_Drones_Forked.
The same file already guards other places correctly:

-- events.lua line 34-40
if script.active_mods["Construction_Drones_Forked"] then
    table.insert(DEBRIS_CONFIG.bonus_loot_table, {
        "Construction_Drone",
        1,
        1
    })
end

-- scripts/message.lua line 145
if script.active_mods["Construction_Drones_Forked"] then
    add_tech("lamp",{ ... supply_drop = {quality = "normal",
        items = {["Construction_Drone"] = 3}} })
end

Only late_memory is missing the check.

Why it does not always crash

create_scaled_rewards filters out zero amounts:

scaled_amount = math.floor(base_amount * pollution_multiplier * yield_multiplier)

With medium pollution (pollution_multiplier = 1.0) and servofish in
healthy state (servofish_multiplier = 1.5):

floor(1 * 1.0 * 1.5) = 1   -> item kept -> crash

With servofish in critical (0.25) or low / overpopulated (0.75):

floor(1 * 1.0 * 0.25) = 0  -> item skipped -> no crash

That is why the crash only appears when the fish population is healthy.

Reproduction

1. Install Eneas 1.0.10 without Construction_Drones_Forked
2. Build on the Eneas surface so that pollution rises above 500
3. Keep the servofish population between 50 and 75 (healthy)
4. Research friend-tech
5. Wait for the next pollution check cycle (15 minutes)
6. Server crashes

Suggested fix

late_memory = {
    tech_required = "friend-tech",
    items = script.active_mods["Construction_Drones_Forked"]
        and {["Construction_Drone"] = {min = 1, max = 1}}
        or {},
}

pairs({}) is a no-op in both build_reward_table (line 752)
and deliver_supplies_to_lift (line 816), so an empty table is safe.

If you prefer to always give something, an Eneas-native item works too:

items = script.active_mods["Construction_Drones_Forked"]
    and {["Construction_Drone"] = {min = 1, max = 1}}
    or {["eneas-artifact"] = {min = 20, max = 40}},

Related: a second missing nil check

prototypes/patches/construction-drones.lua line 15:

local Drone = data.raw.unit["normal-Construction_Drone"]
Drone.run_animation = { ... }

Drone can be nil if another mod removes that unit. Suggest:

local Drone = data.raw.unit["normal-Construction_Drone"]

if Drone then
    Drone.run_animation = { ... }
end

The file is already guarded by if mods["Construction_Drones_Forked"]
in data-final-fixes.lua:7, so this is defensive only.