Op amp current regulator
Perusing the OPA227 datasheet reveals that the common mode range does not include v- or v+. 

It looks like you are using a single supply but your op-amps are not rated for rail-to-rail inputs. The inputs must be at least 2 volts from the rails for it to work.

Exceeding the allowed common mode range will produce all manner of strange results like the ones you have observed.

There are 2 possible ways out.


Use an op-amp with rail-to-rail i/o
Add a negative power supply rail below ground to move ground into the acceptable common mode range.