MS Confusion

["scottsherk27" scottsherk27]

I can't seem to wrap my head around MS and have uncovered a confusing
issue.  I have discovered that after decoding my MS recordings (MDA
plug-in,Voxengo MSED, or Audition) they are 100% out of phase according
to Audition's Phase Analyzer.  When I invert one channel, they return
into phase.  Where in my chain would I inadvertently be inverting the
phasing?  Or does decoded MS always have an inverted phasing?

Thanks,
Scott