Try enabling Unified (UBL) leveling instead of using ABL (Bilinear)
The firmware currently uses ABL and BILINEAR for auto-leveling: https://marlinfw.org/docs/gcode/G029-abl.html
It's possible UBL might produce better results but I don't know how much has to change to swap the two: https://marlinfw.org/docs/gcode/G029-ubl.html