here is a small example of a variator than can stick/stall in certain positions - that worn area should be smooth like the rest of the steel plate.
As there is no spring pressure in the unit it solely relies on oil to advance and retard the unit it cannot be expected to snap back - This design is not like honda vtec to amp up the cam lift etc but more to the effect of reducing pumping losses at mid rpm
When this stalls/sticks you will get some real oddball misfires as there would be an awful lot of backwash into the intake manifold from the cylinders
I need to dig into the wiring/schema of Nissan to see how the ECU is determining the requierd cam phasing is achieved, I know it for toyota - their ECU rely on the cam/tdc sensor difference to determine a problem, if it sees an off TDC situation at idle - it pops the TDC code, which almost always is a stuck variator.