It could be a dodgy side stand switch…

But there’s a well known issue with the neutral sensor on the Honda 500’s - the neutral switch wears down a little every time you go through neutral.

Wouldn’t be too bad, but different systems on the bike read it as ‘in neutral’ or ‘not in neutral’ at different levels, so it gets all kinds of wacky. A common symptom is not being able to start the bike in neutral without the clutch pulled in for example.

It could still be the side stand switch making one of the systems think the side stand is down just at the time of ignition, but yeah, I’ve had issues with that neutral switch at 17 and 43k km’s so I’m leaning toward it being that just from experience. At the end of the day it costs a couple of bucks and you’ll need one at some point.