The mirror select switch setting won't change anything. The problem is that the position sensor potentiometers are dirty and giving bad position readings.
[/rant: If the software guys has spent a little more time on the code for the memory features, they could have compensated for most of the sensor noise and we probably wouldn't even know there were problems with the sensors.]
Both of my LSes have this problem to a degree. I find that if I press the position (one or two) switch several times, the mirrors will move to the correct position. Alternately, you could take the mirror glass off and try spraying the potentiometers with a good plastic safe audio contact cleaner.