I won't vet my answer but VBR (a MP3 encoding) can have issues like this. Your choice to recode the audio to CBR or not.
After I have imported mp3 files from my hard drive into my iTunes (v 188.8.131.52) and play them, I see (and hear) that there is time added to the song length. Not always, but often. For example, a file for a song which is, say, 3m25s long could jump to anything from 3m27s to 3.55s long to 9m55s or even longer.
When I play back the song, iTunes will reach the end of the song at its proper endpoint and then the music loops back to either a few seconds or sometimes even minutes before the endpoint and plays that section of the song again until it reaches the endpoint a second time. Sometimes you literally only get two or three seconds of duplication, but sometimes it really is minutes long.
The original files don't do this when played on a different mp3 player. And when i play the output mp3 file on a different mp3 player, the same problem *does* manifest. So, I assume the files are being corrupted when I am importing into iTunes but I can't work out why. I have been importing songs this way for years and haven't had any such problems until recently.
Anyone else experienced this problem and can they suggest a fix?