Auto-level - First point 27mm higher than all others

Hi all, I’m using the grbl auto-level function and it seems to be doing everything perfectly, except for the first point being at 0.000 and every other point being at about -27. Now, I have some cheap PCB stock but there is no drop of 27mm over a 5mm span. Ignoring the first point at X,Y = 0, the measured curvature of the board seems to be true-to-life the curve of the board. I’ve tried at different zero points, raising the Z=0 of the first point before running it, different board, etc. I’m worried that adjusting my g-code and running it will result in the bit dropping 27mm through the bottom of my machine, so I thought I would ask if anyone had solutions (or knew that it won’t actually change by 27mm) before attempting it. Thanks!

Problem resolved! I was trying this last night, restarting everything and trying again before I finally went to bed with no success. Tried again today and now the second point is only .033mm off - much more reasonable. I have no clue what I did differently.

Were you in any work coordinate system?

I wasn’t aware of using one. I managed to recreate the issue by zeroing out at the correct X and Y, doing a test probe, re-zeroing at the correct Z and starting the run. This gave me a -2mm on the second point and that is about where my Z was before zeroing following the test probe. I know that it saved the correct Z as Return To Home placed the bit exactly at the surface of my PCB. I fixed the issue by leaving the bit at the correct 0 and restarting both my JSON server and Chilipeppr, which then led to a normal auto-level.