@Chris21 said in Mesh bed compensation going wild (Delta):
G30 P6 X0 Y-20 H0 Z-99999 S3
S3 is bad that needs to be at least S6 for 6 factor .
see
https://duet3d.dozuki.com/Wiki/Calibrating_a_delta_printer#Section_Setting_up_the_bed_g_file
also that are not a lot of points.
i would suggest you generate a new bed.g in the configurator.
https://configtool.reprapfirmware.org
try 6 factor first, then 8 then 9 and see if that makes a difference.