Noise stemming from resetting integrator
It is capacitively coupled from the mosfet's parasitic capacitance.  The signal labeled &quot;Integrator&quot; slews too fast for the opamp to react to.  Since there is probably no need for it to be that fast I suggest using the slower version of the signal, taken from C38 and adjust R44 and C38 as appropriate.
An alternative solution may be shunting Q2's drain to ground and adding a resistor between it and V_OUT.
Because of your long ground lead inductance, the spike may be larger than is seen.
Don't leave CMOS inputs floating.  Connect IC8's S̅D̅ to something.