Audio Waveforms Showing on SOME clips, not others

For some reason the majority of my nested sequences are NOT showing waveformed in my timeline.
I have selected "Generate Waveform" under "Clip" for each one.
I do have "Show Waveform" turned on.
There are no apparent differences in the nested sequences between the working sequences and those not showing the waveform. .
The audio works for all of them, but the waveform only shows for about 10% of the clips in the sequence I'm building out.
