Long mp3 files importing at wrong frame rate

I am editing videos of a podcast with a looping video over it. The mp3 files range from 20 - 40 minutes in length. When I import them into Adobe Premiere, the files have an extra 1 - 2 seconds of repeated audio at the end. When I bring them into Audition, they stay the correct length. I calculated the amount of frames the file would have at 30 fps and 29.97 fps and it adds up to the additional seconds. I attempted to change the "Indeterminate Media Timebase" in the media section of preferences to match my file, but there is no change to the file when I re-import it. I was able to convert them to .wav and the issue was solved, but is there a way to fix this rather than converting all the .mp3 files to .wav?