Lip Sync not assigning "W-Oo" viseme to "W" sounds

This is a strange one, but whenever I use the lip sync feature, it leaves any "w" sound blank, instead of assigning the "W-Oo" viseme. I can manually assign the correct viseme, but I can't figure out why Character Animator isn't utilizing it when it processes lip sync.
In the Lip Sync section of the behaviors panel, there are the same number of "W-Oo" visemes listed as the rest (my puppet has three of each, for different emotions), so it's not like the software doesn't recognize it.
What really bakes my noodle is that it will use the "W-Oo" viseme for "ooo" sounds, but not "w" sounds.
Also, I'm using transcripts with the audio files, so it definitely knows that these are w's.
