Side Products of Wacker

[potisgood]

I have been using the ethylnitrite wacker to make ketone, and have been wondering what the side products are.  The pre-distilled oil is black.  I stop distilling after ketone stops coming over, and a good deal (mabey a few grams; < 5 g on the 25 g safrole scale) of black liquid crap is left in the distillation flask which sometimes solidifies upon cooling.  Does anyone know what this could be?  I'm thinking it is either polymerized ketone or a complex of the pdcl2 or cucl2 with organic molecules.

[Panoramix]

The undistilled tar is in my opinion a mixture of palladium complexes, overoxidized and polymerized compounds.
What yield do you get of ketone ? single distilled ?