At least you’re making some progress by achieving uniformity. I still suspect mechanical issues, but I also see possible flow rate inconsistencies in your filament.
Are you using the original extruder that came with the printer? There could be wear in the extruder itself causing flow issues. Filament calibration can compensate somewhat, but the ultimate solution would still be to clean or replace the extruder.
Check out this recent post where someone had similar issues. They shared images of their worn extruder. Their problem involved wall gaps, but the solution might apply to your case as well.
When they finally checked their extruder, this is what they found. It may help to check yours as well. Once they replaced their worn extruder, the issues were resolved.
