Deck won't wake from sleeping

Every time my deck (unmodified 256 LCD) goes to sleep for an extended period, it won't turn back on. Pressing the power button makes it beep, but the screen doesn't turn on and none of the buttons appear to do anything. This is resolved by holding the power button for 10 seconds to reboot the device. I've tried a factory reset, and re-image, but the issue remains. This is a new issue on a 2yr old deck