Hey I also had this problem way back when I just bought the car, I had no idea what was going on...the only way I could get the spoiler to go back down was to re set the car...by that I mean turning it off and then on again. the light on the switch would remain on and pressing the button would do nothing ...
I as well figured it was a glitch and that it would correct its self...but it did happen to me many times...it was not till i took it to get it serviced that I told the dealer about the problem...once I got the car back the tech guy told me it was a glitch and that they had to re-set the computer...that turning it on and off would not fix the problem ...ever since then I have not seen my spoiler go up un less I am going 65 mph! ...hope this helps, I say go to deal and have theme re-set your computer to get rid of the glitch ! ...good luck!