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>