I recommend also to set the bed leveling grid to 7x7 instead of the default 5x5, and set it to measure the maximum 5 samples per point. If you watch the bed leveling and see the printer pause and repeat a measurement of a sample point, that suggests something is under your steel sheet, or a screw or nut got magnetically stuck to the underside of the heat bed and is throwing off the leveling calibration.
Also make sure you dry out the filament. A moisture-contaminated filament flows unevenly, over-extruding sometimes and normal-extruding other times. Put the spool in a sealed container with plenty of fresh dessicant for several days.