Z-Offset non consistent value while using LJ12A3-4-Z/BX NPN

Dear all,
I have an Anet A8 Clone with Skynet V2.0 Firmware and installed LJ12A3-4-Z/BX NPN Sensor by using voltage regulator with 100K and 150 K Resistor.
Starting with leveling the z-offset by preheated bed.
What I didn’t understand is why I got different z-offset distances when homing (without any changes in the system). E.G. Once is start homing and level the bed by using Cura and Command M114 I got e.g -0.7 as needed offset. After saving this value to memory I push x-homing function again and start leveling to check the offset distance. I got other offset distance than before. It is very seldom that the value of distance between triggered sensor and bed remain the same. In case of having wrong offset values I will get bed crashes….
Any ideas what could be the issue? Is this an issue with the sensor or mechanic of the printer?
Cheers,
AGRV

What's the margin of error? Are you doing several readings at same spot?

My advice is to get rid of the voltage divide resistors and use a voltage regulator lm7805.

Like I mentioned in another post, set your layer height and hit print without filament on the printer, once it start printing stop it and measure then use that value as your sensor offset.