Creality Ender-3 V3 KE & SE machines with extreme bed levelling values and large variations can be caused from incorrect standoff locations holding the bed.
The bed used on both Creality Ender-3 V3 KE and SE machines is held with 4 plastic standoffs, of which two are longer than the other two. The height difference is less than a centimeter, but more than enough to skew to the bed and make it difficult to impossible when leveling. Here is a diagram of where they must go:
Essentially the two short standoffs should be placed on the left corners of the bed, the remaining two long standoffs should be on the right corners.