Body composition accuracy

1) After trying all athletic levels on my Smart scale I can report that there was little to no difference in percent calculated.  I found this curious.

2) The real problem is the vastly incorrect measurement of my composition. Smart scale is displaying my composition at between 26.5 to 28 over several months of usage.  These values are almost exactly 2X the measurement by Tania Scales owned by three of my friends.  To evaluate these results, I scheduled a Bodpod measurement which placed me at 13.5%.

How is it after years of usage, Garmin has such a large error in their algorithm?

The question may arise why didn't I return the scale after discovering this inaccuracy?  I purchased it during a move and left it unpacked past the return timeframe.  I wrongly assumed that Garmin would produce a quality product with their background in plane GPS.  Now after dealing with a series of 830 sensor interface issues I've concluded Garmin's firmware department is substandard.  Garmin are you sourcing code development offshore?  Regardless, a quality management system is needed to guarantee firmware testing is adequate?