What is causing the DC Offset in Mirrored Howland Current Pump Circuit
You can't put current sources in series and expect any practical or sensible results. If one was trying to produce 1 mA and the other was trying to produce 1.00001 mA, there'll still be a &quot;fight&quot; and one or the other will win by forcing a DC voltage situation that works. It won't be pretty or useful.
You don't need a differential drive for this - just tie the load to ground and you'll get a bipolar current source providing you are using bipolar op-amp supplies and remember this: -
$$\color{red}{\boxed{\text{Voltage sources in series, current sources in parallel}}}$$