Has anyone experienced intermittent flash during onboard shooting?
It happened with the first HVX200 I had before and I'm experiencing on the second one that I have now.

Here's the clip.
http://www.onebikeguy.com/Kakugyo/P2HD/Pages/HVX200_xtreamcam.html

ND filter shaking? OIS malfunctioning?

I've seen this before from cameras getting knocked around (meaning excessive vibration).

I've never investigated fully because the vibration was my primary problem to take care of...take care of that and the exposure issue goes away.

After watching your clip frame by frame, my hypothesis would be that the iris mechanism is built in a way that makes it fluctuate with vibration...in other words, this a mechanical vibration problem, not an electronic one.

seemed to coincide with bumbs.

Hi,

Well, I guess I just have to tune my suspension to be more supple to suck the bumps then.

I can do that by making the air pressure in the shock and the tires.