I've backlight modded my old GBA - but I've noticed a strange issue that seems to happen randomly. Essentially, sometimes the screen will be 'shifted' up by 1 pixel (i.e. the top row of pixels will be cut off). Usually, turning the system on and off again fixes this. However, I'm not sure why it is happening and whether there is a way to stop it from happening.
A good example for this is the EZ Flash menu (comparison of normal/with issue):
A good example for this is the EZ Flash menu (comparison of normal/with issue):