Sprites random flickering when moving horizontally

Hy.

I have implemented a few sprites that move horizontally on the screen, from right to left. Like in a scroller game.
The problem is there are small lags from time to time. There are some moments when the sprites do not move smooth. They seem to flicker.
It is like the game freezes for half of seconds. This happen at random times. Some times it does not happen and other times there are several spikes in about 5 - 10 seconds.

The fps always stays at 60.
And this problem seems to happen only on windows. It does not happen when I run the app on an ios device.

I change the position of a sprite like this:
sprite~~>setPositionX~~ speed * deltatime );

Any one else had this kind of problem?

Thanks

Did you managed to solve it ? Same problem with me