"Sync to screen refresh rate" leads to extreme jitter in animations

After my upgrade to FotoMagico 4.5.1, I ran into big trouble with my recent slide show. Many of the pan&zoom animations did not run smoothly any longer. There was a strong jitter that was badly visible and ruined many parts in two of my shows last week. Yesterday I finally became aware of a check box in the debug settings to “Sync to screen refresh rate”. I unchecked it, and the problems are now almost gone (although it’s still not perfect).

Is this a new option in 4.5.1? What does it mean after all? I think it should be documented somewhere that this can lead to extreme trouble.

All in all, I have to say I am increasingly disappointed with the reliability of FotoMagico. People do pay money to join my shows, and I cannot afford to disappoint them like this any longer.