Adjustable PMOS current source
I think your problem is that you're loading the output of the operational amplifier with a too big of a capacitive load. These operational amplifiers are generally two pole systems, where the dominant pole is generally caused by the internal node of the amplifier, which has a very high impedance and a capacitor over the second stage to compensate the amplifier. When you add a 150nF capacitor to the output, the nondominant pole at the output will be pushed closer to the dominant pole, reducing your phase margin considerably. However, I was not able to find anything about a maximum capacitive load specification in the datasheet, except in the foreword, which they claim the opamp can drive a 1nF load with a 600Ohm resistor in parallel.

I'd try to lose the capacitor completely, and see how it behaves then.