M500 after G29 Needed?

Hi for some reason my Kossel needs to be tweaked even after the G28 and G29 codes.
It always seems to be towards each side of the Z tower I need to adjust the Bed down a bit.
Then do another print and it has to be adjusted in same spots again, even though the printer does G28 and G29 before every print.
Do I need to include M500 after G29, sorry grasping at straws but G29 does not seem to compensate.

Regards Pete

....Probably should start with telling everybody which controller your using,

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

Someone correct me if im wrong, but running G29 only calls for the printer to generate a correction matrix. It does not permanently save the bed levelling correction, even if you run M500. The moment you home your printer, the correction will be gone and you need to run G29 again before the next print. But i think that it can be done though. Take a look at this.

*assuming that you are using ramps with marlin firmware

I only get this when running G29.. no mention of a correction Matrix?
3.03 3.28 3.35 3.34 3.29 3.17 3.04 2.75 2.46
3.08 3.23 3.39 3.42 3.40 3.30 3.09 2.89 2.63
3.21 3.34 3.43 3.50 3.50 3.44 3.31 3.09 2.87
3.32 3.46 3.60 3.67 3.71 3.66 3.55 3.39 3.17
3.42 3.58 3.74 3.82 3.86 3.82 3.77 3.65 3.48
3.56 3.72 3.87 3.95 3.93 3.95 3.93 3.85 3.72
3.70 3.79 3.89 3.96 3.95 3.94 3.97 3.93 3.93
3.79 3.84 3.89 3.94 3.89 3.87 3.90 3.89 3.93
3.87 3.89 3.88 3.76 3.68 3.69 3.79 3.85 3.92

Sorry I'm running Ramps 1.4 board.

The correction matrix is automatically applied to your printer and will stay in effect until the next homing. That is why you are able to print flat after running G29 and have to rerun it befor every print. Check the link i posted to save the correction to eeprom. Havent tried it myself though and i think not everyone would recommemd it.