Did you try to clean your extruder gears?

Check the filament: Is the extruder gear biting too hard into it causing the gears to grind and slip? Is the extruder gear not biting enough into it causing it to not grip enough and slip? Are the extruder gears maybe worn down and don’t grip well anymore?

WIth all the things you did so far, I’m close to sure that your issue is with the extruder gears being dirty, worn or the extruder gear pressure being too weak or too strong.