[sdiy] Bizarre Xpander Tuning Problem

[gm]

I have here an Xpander that will either pass or fail Tune, but will 
always have the VCO 1s in perfect tune & scale, while all six VCO 2s 
will be out of tune & out of scale.

Did the usual replacement of all DAC components, and the ICs involved in 
the tuning routine;  no help.

Am struggling to find what all six VCO 2s have in common that might be 
causing this;  any pointers would be greatly appreciated.

~GMM