Varying results from G29, inconsistent with M48

[Roxy]

First... Your M48 numbers look good! You should be able to do Auto Bed Leveling!

Second... On those multiple G29 runs... You should do a G28 immediately before a G29. The reason is you don't want to be running G29 in a 'corrected' coordinate system. There is debate on this point but right now, do a G28 before a G29. And if you compare the G29's at that point I suspect they are going to correlate better.

M48 doesn't care about the Z=0.000 point. It just gets close to the bed and measures what the current coordinate system is giving. M48 is only measuring the repeatability of the Z-Probe (under different circumstances). I am fixing the M48 code to work for Delta's. And one of the things that might carry over for the Cartesian printers is this: M48 probably should operate in an 'UnCorrected Coordinate' system. That is not the case currently. It doesn't really matter but it does cause confusion like this.

G29 is trying to construct a new coordinate system that will result in 'flat' moves across the bed for a given Z number. There is a lot of discussion about how G29 should do that. But at the end of the day, G29 needs to add in the values probed to its offset. You get debate whether it should be a point from the center of the bed or the mean of all points. You also get debate about whether the Z-Probe Offset should be factored into the Z equals 0.000 point. It is a very complicated subject. And in fact, Delta's do Auto Bed Correction differently because they have extra issues with the bowl shaped coordinate system.

Did you try applying your Configuration.h file to the BeckDac fork? I suspect it is going to work very well for you. If you bring up the BeckDac fork you can ignore all the other Auto Bed Leveling talk until things get resolved.