Sound likes it's playing the sample at Nuendos preset tempo which is probably 120bpm. U may have to set Nuendos tempo before you import the sample in the way that you are. Acid Pro does that to me depending on how I import the sample. When I bypass the beat mapper is when it usually speeds shit up. Adjust Neundos tempo to the samples original tempo or the tempo that you're going to use the sample and you should be str8.