Hi Yunsong,
T2 (middle pin) is actually the negative input, while T2 (bottom pin) is where the return currents from the IR1 / IR2 reference current signals flows. So the real effect of lifting the middle pin is that the negative input will go to the compliance voltage of the IR2 source and will be much higher than the positive input which should cause the output to go to 4mA. I don't see how doing this would affect the power-supply voltages.
When you measure the power-supply voltages, what are you measuring between? i.e. what electrical nets are the black and red probes connected to?
I don't care for the inductor between the isolated and non-isolated GND potentials. If you remove the inductor, does the issue go away?
Does this issue in any way affect the operation of the circuit?