How to fix the error "FunctionName is not a valid member of ModuleScript"?

[threethirtysevens (Ubiquinone)]

I have the following server script calling other module scripts in order to create bossfight attacks.

local nextevent = script.Parent.NextEvent
local atktable = {}
for _, v in pairs(script.Parent.Attacks:GetChildren())do
	if v:IsA("Folder") and v:FindFirstChild("AttackBehaviour") then
		require(v:FindFirstChild("AttackBehaviour"))
		table.insert(atktable, v:FindFirstChild("AttackBehaviour"))
	end
end
local function useAttack()
	atktable[math.random(1, #atktable)]:startAttack()
end
useAttack()
nextevent.Event:Connect(function(param)
	if param == "UseNext" then
		useAttack()
	end
end)

Within the AttackBehaviour modules, it looks something like this:

local module = {}
local ShootTurret = require(game.ReplicatedStorage.AttackPresets.ShootTurret)
local nextevent = script.Parent.Parent.Parent.NextEvent
function module:endAttack()
	for _, v in pairs(script.Parent:GetChildren())do
		if v.Name == "FireEffect" then
			v:FindFirstChild("ParticleEmitter").Enabled = false
		end
	end
	nextevent:Fire("UseNext")
end
function module:startAttack()
	print("Attack2")
	for _, v in pairs(script.Parent:GetChildren())do
		if v.Name == "FireEffect" then
			v:FindFirstChild("ParticleEmitter").Enabled = true
		end
	end
	ShootTurret:shootBullet(script.Parent.Turret, 250, 10, 5, Color3.fromRGB(45, 144, 206), nil)
	task.wait(0.5) 
	module:endAttack()
end
module.startAttack()
return module

The modules run succesfully (i think?) twice until it returns the error. module:startAttack() and module.startAttack() makes no difference

[C_Sharper (Sharpie)]

I believe you actually want to store the required module (table returned from the require call) into the table instead of the ModuleScript object:

local nextevent = script.Parent.NextEvent
local atktable = {}
for _, v in pairs(script.Parent.Attacks:GetChildren())do
	if v:IsA("Folder") and v:FindFirstChild("AttackBehaviour") then
		
		table.insert(atktable, require(v:FindFirstChild("AttackBehaviour")))
	end
end
local function useAttack()
	atktable[math.random(1, #atktable)]:startAttack()
end
useAttack()
nextevent.Event:Connect(function(param)
	if param == "UseNext" then
		useAttack()
	end
end)