In my experience, it’s usually something mechanical. My SV650S was doing that, and I took apart the entire clutch perch and cable and lubed and cleaned everything and installed it properly and neutral was there clear as day all of a sudden. Not sure what the exact culprit was but it was contained somewhere in that clutch cable system. Also, the oil LEVEL can make finding neutral difficult if it’s not in the right range. Oil types though, I dunno..