Product review (5 stars): Lots of SD and F21 codes? Replace pump motor.
If your machine was like ours, our pump never died, but we increasingly experienced SD and F21 codes, related to slow draining.  That meant frequent re-washing (or at least drain-spin).

If the center of your pump (the blade-rotor) has any wiggle, your motor is wearing out and inefficient. (*How to check? While unplugged, remove the drain trap (for catching debris) and reach your finger in toward the pump.  Besides normal rotation, you should not be able to wiggle it at all.)

Product was perfect fit.  Best price.  No tools required.  Pump twist-locks into place.  Note, product includes connector wires to accommodate wire-harnesses.  No biggie, connects by hand.

For first time in years, machine running like new.  No codes for the first 21 loads and counting!