I am trying to use Audacity record a weekly radio program that I used to do in the studio. The system crashed on me when I used WAV files, so now I’ve converted the audio files to MP3. My latest problem is that the files play back simultaneously rather than sequentially. I used the align tracks end to end command and saved the project after doing so, but the problem continues.
Do you know why this happened ?
file or files ? 
OK, so I just created a stereo recording, then split it up into 3 clips and moved the second two clips to the start of a new track. I then did Tracks > Align Tracks > Align End to End, selected ALL of the audio (Ctrl+A), then Exported to MP3.
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When I imported the result, it played just like the original recording. (it was actually all of.03 seconds shorter that the original).
Everything seems to be working OK for me. Did I misunderstand what you were trying to say?