Strange mouse offset happening?

I am currently making a grid placement system but some strange offset is happening to the model I am trying to move inside the baseplate.

Take care, this is a moduleScript.

Placement_Handler.RoundByThree = function(Number)
    if math.floor(Number) == Number then
        if Number%3 == 0 then
            return Number
        elseif (Number - 1)%3 == 0 then
            return Number - 1
        elseif (Number + 1)%3 == 0 then
            return Number + 1
        end
    end
    return Number
end

Placement_Handler.placeModel = function(plrMouse, modelVisual, modelHitbox)
	local LastPosition = CFrame.new();
	while true do
		if plrMouse.Target then
			if plrMouse.Target.Name == "main_Base" then
				local mainBase = plrMouse.Target;
				modelVisual.Parent = mainBase.Parent;
				
				local mainBaseSizeX, mainBaseSizeZ = mainBase.Size.X, mainBase.Size.Z;
				local hitboxSizeX, hitboxSizeZ = modelHitbox.Size.X, modelHitbox.Size.Z;
				
				local mainBaseTopLeft = mainBase.CFrame * CFrame.new(Vector3.new(mainBaseSizeX/2, 0, mainBaseSizeZ/2));
				local baseAngleX, baseAngleY, baseAngleZ = CFrame.new(mainBase.Position, (mainBase.CFrame*Vector3.new(1, 0, 0))):toEulerAnglesXYZ();
				local VectorRotation = CFrame.Angles(baseAngleX, baseAngleY, baseAngleZ);
				
				local RoundByThreeX = Placement_Handler.RoundByThree(plrMouse.Hit.p.X - mainBaseSizeX);
				local RoundByThreeZ = Placement_Handler.RoundByThree(plrMouse.Hit.p.Z - mainBaseSizeZ);

				if RoundByThreeX < -mainBaseSizeX + hitboxSizeX then
					RoundByThreeX = RoundByThreeX + hitboxSizeX;
				elseif RoundByThreeZ < -mainBaseSizeZ + hitboxSizeZ then
					RoundByThreeZ = RoundByThreeZ + hitboxSizeZ;
				end
				
				local VectorComponent1 = CFrame.new(Vector3.new(mainBaseTopLeft.X, plrMouse.Target.Position.Y, mainBaseTopLeft.Z));
				local VectorComponent2 = CFrame.new(Vector3.new(RoundByThreeX, plrMouse.Target.Size.Y/2, RoundByThreeZ))* VectorRotation;
				local VectorComponent3 = CFrame.new(Vector3.new(-hitboxSizeX/2, modelHitbox.Size.Y/2, -hitboxSizeZ/2));
				
				local NewVector = VectorComponent1*VectorComponent2*VectorComponent3;
				
				local RegionVectorMin = NewVector * CFrame.new(Vector3.new(hitboxSizeX/2, -modelHitbox.Size.Y/2, hitboxSizeZ/2)); -- TopLeft
				local RegionVectorMax = NewVector * CFrame.new(-Vector3.new(hitboxSizeX/2, -modelHitbox.Size.Y/2, hitboxSizeZ/2)); -- BottomLeft / Counterpart
				
				local Hitboxes = game.Workspace:FindPartsInRegion3(
					Region3.new(
						Vector3.new(
							math.min(RegionVectorMin.X, RegionVectorMax.X),
							math.min(RegionVectorMin.Y, RegionVectorMax.Y),
							math.min(RegionVectorMin.Z, RegionVectorMax.Z)
						) + Vector3.new(0.1, 0, 0.1),
						Vector3.new(
							math.max(RegionVectorMin.X, RegionVectorMax.X),
							math.max(RegionVectorMin.Y, RegionVectorMax.Y),
							math.max(RegionVectorMin.Z, RegionVectorMax.Z)
						) - Vector3.new(0.1, 0, 0.1)
					), nil, 100
				)
				
				local ModelColliding = false;
				for i, Hitbox in pairs(Hitboxes) do
					if Hitbox.Name == "Hitbox" and not Hitbox:IsDescendantOf(modelVisual) then
						ModelColliding = true;
					end
				end
				
				if not ModelColliding then
					LastPosition = NewVector;
				end
				modelVisual:SetPrimaryPartCFrame(LastPosition);
			end
		end
	wait();
	end
end

It literally does this weird offset: Click here!

Help would be appreciated!