Try running the program in a window (rather than full screen) sized to show the entire BIAB program window and see what you get. Also try setting the number of rows displayed in the chord sheet to a higher value, and while you are at it try changing the font for the chord sheet. Be sure you are using the latest drivers for your video card. Finally there is the old tried and true return to factory settings and/or a reboot of the computer.
Good luck.