Placement system is out of grid sometimes??

So im basically trying to recreate "Build to survive the zombies". But i ran into this problem with my placement system. Its out of grid sometimes.

My gris size is 4x4x4

My block size is 4x4x4

My plots size is 110, 0.1, 110

Heres a video showing a bit more of what i mean: https://www.youtube.com/watch?v=gW5nl1tIkws

This is my code that handles movment:

if RAY then

                    CAN_PLACE = true
                    local X = math.floor(POS.X / 4 + 0.5) * 4 -- // POS is the rays hit position
                    local Z = math.floor(POS.Z / 4 + 0.5) * 4
                    local Y = math.floor(POS.Y / 4 + 0.5) * 4


                    local NEW_CF = CFrame.new(X, Y, Z) + (SURFACE * (CURRENT_OBJECT.PrimaryPart.Size * .5))

                    CURRENT_OBJECT:SetPrimaryPartCFrame(NEW_CF * CFrame.Angles(0, math.rad(CURRENT_OBJECT.PrimaryPart.Orientation.Y), 0))

                end