Placement system weird behavior?

So ive been experimenting with placement systems for about 1 month now. But i recently encountered this problem while making my own placement module.. The problem is that when you change the grid to anything higer than 2 it kinda wont stick to any blocks.. Here are two videos showcasing what i mean.

Grid size 2 https://www.youtube.com/watch?v=_5UMY9dOGhQ

Grid size 4 https://www.youtube.com/watch?v=W-wpUS9rwsU

Heres the code i use to calculate the cframe:

function CAL_CF(POS, SIZE) -- // POS is the raycast position and SIZE is the current blocks size
    return CFrame.new(
        math.floor(POS.X / SIZE + 0.5) * SIZE,
        math.floor(POS.Y / SIZE + 0.5) * SIZE,
        math.floor(POS.Z / SIZE + 0.5) * SIZE
    )
end

Positioning the block

function placement:Enable(Name)

    local Block = Blocks:FindFirstChild(Name):Clone()
    Block.Parent = self.PLR.Character
    OBJ = Block

    MOVE = M.Move:Connect(function()
        local POS, SUR = RAY({self.PLR.Character})

        if POS and SUR then
            local CF = CAL_CF(POS, self.SIZE)
            Block:SetPrimaryPartCFrame(CF + (SUR * (Block.PrimaryPart.Size * .5)))
        end
    end)

end

My block size is 4x4x4 if you need that.