This is caused by cue points, tempo and root note information being stored in the sample. It is ignored by the previewer but used in the sample player.
There are a few ways of correcting the problem. First you can disable the various settings in the FL channel properties that use these cue points, tempo and root note data.
Here is a video from Warbeats that shows how it's done:
the second way is to run a program to remove the points and resave the sample without them. This would be very useful if you find that a drum kit you are using has a lot of these embedded points.

To make a great program even better, you can donate to the developer and he'll send a proceed of that money to the relief effort in Haiti. How great is that!
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