Problems with battery discharging circuit

[Harneet]

I have a circuit that aims to discharge a battery and hence monitors it's voltage.
The circuit either drains 4 uA current through a 680k resistor or 20mA current which is driven by the DAC. The switching between these two scenarios is done using a 74hc125 ( have tried N FET as well)

The circuit diagram is attached.

Problem: When the switch corresponding to 680k is enabled it gets grounded but when switch corresponding to 10 ohm resistor is enabled it doesn't gets grounded.
I'm unable to spot the problem with the circuit .
Please help!!

[bwetman]

I think there is some problem with the hardware not with the software.