The circuit looks strange, the purpose of Q1 and Q2 is mysterious.
A basic constant current circuit would connect the OP output directly to the gate.
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P.S.: Reviewing your initial post, we can just guess that the strange transistors have been added to fix a circuit problem, but you didn't tell what it is. Similar to the problems reported before, I presume it's rather a simulation related than a real circuit problem.
If you want others to reproduce and possibly fix the simulation problems, you should post the LTspice circuits, either zipped or the *.asc files renamed to *.txt.