Problems with Sine function in material editor

Hi, I am having a problem with my Sine function in the material editor. I followed this tutorial on making a water material rise a fall, to simulate waves.


But instead of moving normally my material jumps up and down with no clear standard period. I hit the review button and unlike the tutorial instead of seeing a long white pule followed by a dark pulse of equal length I see multiple long white pulses followed by short dark pulses and every 4th white pulse is followed by 2 dark pulses? My setup is exactly the same as in the tutorial.

I reloaded the map the next day and found out that now it is working ok.