Whenever I import mp3's, the audio cuts off in Premiere. I've found a way to fix it, but it takes up so much of my time when editing and I NEED to find a way to fix this permanently. I've been uploading these files to my Adobe Cloud, if that's relevant.
On my Windows machine I always drop an mp3 onto the Media Encoder icon and then convert it to wav. mp3's are like using h.264 video files for editing. The computer needs to work to uncompress the file while using it. Wav's are like ProRes or Cineform, they are already basically uncompressed to begin with, so take less umph... from your machine.