mp3 import cuts file length

Hello, I have the same problem. Cubase 7.5.40. All preferences are correct. When i’m trying to make a loop in DAW - its perfect. I export file, then import it back to Cubase and it’s croped. I have no idea what is wrong. It happens mostly with mp3 but sometimes with Wav too. Mp3 files import cuts very hard, sometimes up to second. Any solutions guys?