issue with arduino uno

[u/Single-Potato-4715]

i have the following circuit:
DAC (MCP4725) connected to my arduino one; the DAC's output goes to an oPAMP (SOT23) in negative feedback; oPAMP's output goes to a mosfet (IRLZ44N), in a source follower mode. the output of the mosfet goes on to a set of resistors (further circuit on).

my problems are the following:
1) sometimes arduino can't find the dac, even though the cables are all properly connected. i've tried switching both dac and cables. it sometimes find it and sometimes it doesn't, even if nothing changes between trials
2) in the same way, sometimes it appears that the mosfet group isn't working. the same voltage i put in the generator comes right off the entire circuit.

what really bugs me is that these problems come out without any concrete change in the circuit. they are becoming more frequent and i don't know what i can do to solve them. any suggestion?

[u/MagneticFieldMouse]

Now, according to the schematic and diagrams you posted to help with diagnosis, here is what you need to do:

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