K-7 Missing RAW levels

Does anyone know why the .pef raw files from the K-7 have missing (zero) levels in the original (unmapped) data ?

This seems to be independent of ISO, every 7th or 8th histogram bin appears to be zero.

Raw Histogram 0-128 bins

Plotted with RawDigger. RawAnalyze shows the same effect.

The original .pef file is at https://docs.google.com/open?id=0Bzp4tAu_4Sv5TW9IdnlpcC1lZVU

I've searched through the forums but no-one seems to have noticed this before.

Thanks.