This issue (unrelated to the F1-F3 keys, which adjust the speed of the game and are working as intended) can be caused by having a high refresh rate monitor. Disable Vsync in game. If the game crashes when disabling Vsync, go to Documents\My Games\FINAL FANTASY XII THE ZODIAC AGE\<number>\GameSetting.ini and change VSync=On to VSync=Off
Documents\My Games\FINAL FANTASY XII THE ZODIAC AGE\<number>\GameSetting.ini
The game has an option to run at different speeds by pressing the F1-F3 keys. Press F1 to return to default speed.