Ditto on Ed's commentary. I've had mine sieze up once - no fun trying to get an angle on it to see what's haywire.
Open the tray and check the slide runners with a flashlight, preferably a bright LED one, for debris in a track. And check that a roller hasn't slipped its track and is jamming. Hopefully you won't have to remove all the batteries to get to the bottom of it. It's never a convenient time for these issues, which is why I try to detergent spray, rinse, let air-dry on a warm light-wind day, and dry silicone spray those components once in a while.
Joel