Premiere processes material on the timeline using its own CODEC list, whereas the clip windows use Windows facilities.
If a clip plays OK in Media Player etc, but not in Premiere, it is likely to be a CODEC issue. If you lose just the sound, it could possibly be a change of sampling rate at the cutoff point if camera settings were changed.
If razoring the clip at the point where audio is lost doesn't restore full audio, you may need either to recapture the clip or to process it outside Premiere.
Alternatively, if you have applied any audio FX, try without. Conversely, if none are applied, try something benign and see if Premiere's rendering of the audio cures the problem.