I have a new GMC-320. When in the menu to select the display type, the unit "times out" before I can press the up or down buttons to scroll through the choices. Can this timeout be changed, or is this maybe a known issue? Further, sometimes, the display type will spontaneously change from one to another, eg. if I am in large font and testing a sample, it will frequently simply change to either text or graphic without my input. I have even seen it almost scroll through all three choices while testing. Any ideas? Thanks