Greg, the amplitude adjustment mod may be of help here. It allows adjustment of the gain from around 3:1 stock to around 1:1 at the low end. This still keeps the low impedance drive but cuts the amplitude of the signal to about what the command base outputs.
DM TMCC Buffer Gain Adjustment Modification.pdf
This may solve the issues you're seeing. Jon Z. noted that the LCS Sensor tracks have a problem if they get too much signal, could be the DZ switch machines have the same issue.