Hi, have you used any of the buttons on the monitor rather a lot (like the one for the auto adjustment or volume control or brightness or......)? I have seen some where the buttons got sort of stuck halfway out, having lost their flexibility due to being pushed a lot. Another reason causing the same symptom could be dirt/dust preventing it from really releasing the contacts reliably. Best would be to find the button that really causes the problem and either clean it and the front bezel of the screen or replace it with some cannibalized fitting spare from some old dead monitor's control panel.
I had exact the same problem... the "FUN-OSD" always appeared randomly.
As I already broke the Button out with a screwdriver I wasn't able anymore to send it back (for free).
The problem appeared again today and I opened up the display, now I took out the panel with all OSD-Buttons and left the connector unconnected in there. Then closed it again and tested.
Bad news: It is still popping up.
So even it is an OSD control which is showing up, it is not the OSD panel. Maybe it is a bad cable or something....
My conclusion on this is so far only <b>never again LG</b>