Auto Leveling not maintaining even gap

I pulled the latest Marlin firmware and still the gap on the extruder is on the glass on the left side .1mm in the center and .3mm on the right.

I do a G29 and have it probe 9 points on the bed then check the gap.

Using Ramps 1.4 and Pronterface 2014.04.06 on a wooden frame Prusa i3

I have seen it work in videos but so far it doesn't hold up to the auto leveling name for me.

#define ENABLE_AUTO_BED_LEVELING // Delete the comment to enable (remove // at the start of the line)

#ifdef ENABLE_AUTO_BED_LEVELING

// There are 2 different ways to pick the X and Y locations to probe:

// - "grid" mode
// Probe every point in a rectangular grid
// You must specify the rectangle, and the density of sample points
// This mode is preferred because there are more measurements.
// It used to be called ACCURATE_BED_LEVELING but "grid" is more descriptive

// - "3-point" mode
// Probe 3 arbitrary points on the bed (that aren't colinear)
// You must specify the X & Y coordinates of all 3 points

#define AUTO_BED_LEVELING_GRID
// with AUTO_BED_LEVELING_GRID, the bed is sampled in a
// AUTO_BED_LEVELING_GRID_POINTSxAUTO_BED_LEVELING_GRID_POINTS grid
// and least squares solution is calculated
// Note: this feature occupies 10'206 byte
#ifdef AUTO_BED_LEVELING_GRID

// set the rectangle in which to probe
#define LEFT_PROBE_BED_POSITION 50
#define RIGHT_PROBE_BED_POSITION 195
#define BACK_PROBE_BED_POSITION 185
#define FRONT_PROBE_BED_POSITION 50

// set the number of grid points per dimension
// I wouldn't see a reason to go above 3 (=9 probing points on the bed)
#define AUTO_BED_LEVELING_GRID_POINTS 3

Edited 1 time(s). Last edit at 04/25/2014 12:36AM by randyf1965.

Would homing to to the wrong location cause this? I currently home to the left rear corner of the bed, which I am now seeing is wrong. I will change home to the front left corner and test when I get home.

I recently switched from a Sangiunololu to a Ramps 1.4 and love the ramps compared to the Sanigunololu.

Edited 1 time(s). Last edit at 04/25/2014 02:33PM by randyf1965.

I adjusted the Y axis homing so the front left corner is home and still the right side of the bed has a larger extruder gap than the left. I see the z-axis steppers spinning as it moves from left to right

I printed new Z axis couplers to see if they were slipping slightly.

Standard deviation over 10 probings (G29):
front left .036mm
front right .019mm
rear right .034mm
rear left .025mm

But the extruder is .6mm TOO low on the left and .3mm TOO high on the right!!

Is the G29 the correct gcode for Marlin?

what is planeNormal x: 0.02 y: -0.00 z: 1.00 ? After every G29 it is the same