If it's full of water maybe it's not draining out fast enough and then when you put it on a rinse and spin cycle it has time to finish draining.
I would take a look at how fast it drains. Pull the hose up out of the stand pipe just far enough so you can watch it drain. Sometimes the drain hose will reach a laundry sink near by that you can drain it into well you watch it.
If it's not pumping out full force then it's time to look for restrictions in the hose or pump.
Let us know if you have any other questions.
Keep us updated on what you find, thanks.