Script won't select right part?

I'm making a cannon that targets the NPC, and damages the NPC over time. Here's the script:

a = script.Parent 
local cbest = 1000
besti = game.Workspace.Units.back--Furthest block from point (purposely set)
for i,v in ipairs(game.Workspace.Units:GetChildren("Warrior")) do --Finds all parts in "Units" named "Warrior"
local p = (v.Parent.Warrior.Torso.Position-a.Position).magnitude
if cbest > p then 
cbest = p
besti = v
end
end

print(besti)
while true do
	wait(3)
	besti.Humanoid.Health = besti.Humanoid.Health - 2 --Hurts closest found Humanoid
end

w = besti.Humanoid

w.Changed:connect(function()
	if w.Health <= 0 then
		game.ReplicatedFirst.Attack:Clone().Parent = script.Parent --Deletes this script, and copies -it again from ReplicatedFirst so that the process can be repeated (If their are multiple enemies)
		script:Destroy()
	end
end)

The problem is that it keeps selecting the part "back". Now, the purpose of "back" is to set the furthest possible point that the NPCs can be, that way it can create a boundary without going over ROBLOXs "no further than 1000 studs rule" with Magnitude. "v" is supposed to be an NPC "warrior" selected from the holding model "Units". However, it appears that "v" is not selecting any warrior to become "v", instead it is remaining blank. So, when it comes time for "besti" (which is supposed to be the closest NPC) to be determined and have health removed from it, "besti" is still "back", as "besti" is also used to determine "back" earlier in the script.

I've been trying to figure out whats wrong for hours now, and I feel like its something so stupidly obvious, and I'm just blind.

Any help?

GetChildren does not take an argument. Writing GetChildren("Warrior") does nothing extra. You seem to think it gets all descendants of an object with the name of the passed string, but it does not do anything like that.

You also write v.Parent.Warrior which is strange because I presume the actual name of v is "Warrior" so it would just be getting the first object named "Warrior" in the set of units and checking the same distance repeatedly.

Raycasting has a length restriction of 1000 because it would otherwise place heavy calculations on the engine whenever a ray was cast that did not collide with anything. The number "1000" is not a constraint to all arbitrary numerical values.

Instead, search through every index of Units and check if the name is Warrior. Calculate the distance from their Torso.

local cbest=math.huge
local besti=workspace.Units.back
for _,v in pairs(workspace.Units:GetChildren())do
	if v.Name=="Warrior"then
		local p=(v.Parent.Warrior.Torso.Position-a.Position).magnitude
		if cbest>p then
			cbest,besti=p,v
		end
	end
end