@User My expectation is that if the problem is with the start up circuit then the gate of the mosfets within the core of the bandgap will be pulled to vdd (this never happened for me) ,but i found that sometimes the simulator solves the dc sweep on supply correctly (when inverting the sweep from maximum to minimum) although it solved wrong operating point which is used in ac simulations i need to measure the psrr which is the reason why i use nodeset also note that despite using nodeset the simulator fails to solve at some corners