are you using the playlist area (in the right) or just playing it in the beat step sequencer. You have to drag the sample to the playlist area of FL studio, where it'll make a wave form. Place it anywhere you want in the song (that you building in the playlist area)
I think it's called the playlist, it's the area you build the track on the right side of FL.
If you use the sample like you making a beat in the step sequencer, ya it will repeat. I dont work on samples in the step sequencer. I always drag them directly into the song and put them into their own mixer track to mix separately with...
Does that make sense? What exactly are you doing to make it repeat?