With the F4, I'm not sure what causes upper LCD bleed, but lower LCD bleed typically is caused by impact damage. F3 bodies typically don't leak, but instead have issues with either extra digits showing up, scrambled digits (typically a loose connection), fading, or no LCD display at all. The F5 is like the F3, in that sometimes the LCD will just disappear either partially or completely in the viewfinder. I haven't seen any leakage on that LCD, but, have on the top and back LCDs. Not enough experience with the F6, plus it, like the F100, uses negative LCD displays in the finder.