Per your tweet, the sample file is here: https://t.co/bCfW2Y27z0
My original guess is that the chunk sizes are probably wrong on the file. There's a number of good tools out there that can validate RIFF WAVE files. Audition tries to be very accomodating when opening potentially malformed audio files, but the shared code to harvest XMP metadata is more pedantic (for good reason). If you open the file in Audition using the libsndfile importer plug-in, you'll see this information dumped out into Audition's log file:
File : ~/Desktop/XMP/wavFileXmp.wav
Length : 12657
RIFF : 88854 (should be 12649)
WAVE
fmt : 16
Format : 0x1 => WAVE_FORMAT_PCM
Channels : 1
Sample Rate : 44100
Block Align : 2
Bit Width : 16
Bytes/sec : 88200
data : 88200 (should be 12613)
End
Notice that libsndfile is mentioning that the size reported in the RIFF chunk (88854 bytes) is much larger than the actual size of the file (12657 bytes). So this file isn't well-formed and is truncated.
There are a few good tools I'd recommend to make sure your WAVE files are both well-formed and valid: