Audio track ends in diferent time acording to time I start to play it.

I had audio file in my project. I wanted to cut out some part, therefore I split it in three pieces and removed the middle, then I placed the third after the first.  I made sure that I split audi in right place. Now, when I play the first audio track close to the end, it ends on right time and another track immedietely follow. But when i start to play the audio a little bit closer from start, the first track is incomplete and seccond track starts to soon. When I play totaly from start, It is reduced even more. When I convert the file into movie, problem remains. What can I do?