Some audio disappears on import (Premier Elements 12)

I have Premier Elements 12 installed on my PC and am using Windows 10. When I imported a large (4+hours, 4GB) wmv file into a new project, I got audio for the beginning of it at first, but a few minutes in the audio disappeared. Also after trying some edits, the audio that had been present in the beginning went missing and there was no audio anywhere. I closed the program and re-opened, then made a copy of the original wmv file, renamed it, and imported it into PE12 (hoping any cached files from the previous project/import wouldn't mess it up) and this time no audio was present anywhere. I tried saving/exporting clip of this file from PE12 to see if the audio showed up in the saved export and it did not. I then imported 2 small AVI files taken on the same device as each other with the same settings as each other and stored in the same folder, and there is no audio at all on first one of them (in PE12), but the second one's audio works fine. More recent m2ts files import with audio so far. Help? Thanks.