Faffed up bleeding can make it worse or at least just a waste of time.
First thing is to check the pressure. It must be bang on 250psi.
Another thing is loosen the seat clamp a little and see if that makes a difference. They are affected by overtightening the clamp. Use some carbon assembly paste to reduce the clamp torque required to stop it slipping.
If these fail, try bleeding.
Though I’ve got an old one that’s both slow to return and tough to drop as it needs a lot of force. Done all the above and bled it numerous times just to be sure I wasn’t messing it up, but not fixed. Ended up getting another as needed one asap. I’ve got yet another on the hard tail which has been fine though recently it’s getting a bit tough to make it descend. Returns fine though.