Distortion (not clipping) introduced on import to iTunes

I have been importing lots of vinyl recorded in Audacity into iTunes without a problem, but I just had about 500 msec of a song import with distortion.The attached file shows the spectrogram of the section that shows primarily in the left channel evidence of damage to the record.
Distortion Section_Fotor.jpg
Ordinarily this type of spectrogram would likely sound distorted on playing, somewhat like clipping–there is no clipping in this recording. However in this case, this section does not sound distorted upon playing the vinyl or after recording and playing it in Audacity. I have had several records that show this type of damage and the resulting audible distortion upon playing. However, in this particular case it is not audible in Audacity, but only after exporting the file as AIFF from Audacity and importing into iTunes. Why would this section sound fine in Audacity but not in iTunes?

I am recording in Audacity 2.1.1, “exporting multiple” AIFF files, and importing these without other conversion into iTunes using Mac OS X 10.7.5.

If you play the exported AIF in some software other than iTunes (quicklook [select file and press spacebar] would do), do you hear the distortion? If you import the AIF into Audacity and play it back, do you hear the distortion?
– Bill

Oh my! Now my iTunes import is NOT sounding distorted like it did when I first imported it. It must have something to do with the computer or playback conditions at the moment it is being played. I guess the damaged section in question is marginal, and if the computer is short on memory, or having to access other programs running, or some other thing that happens inside this mysterious black box called a computer, the damaged, marginal section will sound distorted. Today it plays just fine.

Also after bringing the iTunes file into Audacity, the distortion is not audible when playing it in Audacity.