Z_PROBE_HEIGHT is not distance when deployed but distance when triggered which is normally less.
Z_PROBE_SWITCHING_DISTANCE is for repetitions and you will get an error message if it does not untrigger (at least with dev version).
You should also note that especially for deltas z=0 is not the same over the bed. This depends much on geometry defects and values entered as correction. So what you normally do is using Repetier-Host, make G32 S2, go down to Z= z probe bed distance and start measuring height map. You will see how much it goes up/down and if there is a pattern and correct geometry correction to reduce the errors if required. As a last resort you would use G33 to make first layer stick better.
