It could be due to a bit of corrupt or unreadable data 70% of the way through the file.
Are you reading the file off a flash card / thumb drive?
Does the file play all the way through, or does playback stop 70% of the way through?
Thanks for the responses. I looked into other options and found MP3DirectCut a lot easier to use for big files–no import times at all. I’ll use that to cut the files down to smaller ones and then process in Audacity.
MP3DirectCut doesn’t need to do any complex processing
The down side of that is you can’t do anything to the sound while it’s inside the software. All you can do is cut and paste. There are no production tools. If that’s your goal, then MP3DirectCut is for you.