When I turn it up, it turns down

Maybe you're holding the remote backwards. My wife does this all the time. ;)

I would email the NAD North American Distributor. Send a very detailed description of everything involved with what is happening when the M3 does this. Ask NAD if they have any feedback/suggestions. If you ultimately need to have the M3 serviced to solve this issue, NAD has authorized service centers they can refer you to. Keep the NAD North American distributor aware of every step you take. NAD can be very helpful in these situations.

The above recommendation is if you can't fix the issue with the suggestions given to you in this thread. If any of your fixes don't work out, I would contact the authorized NAD service center recommended by the NAD Distributor, let them diagnose the problem, and then email the details of the repair and cost to the NAD Distributor to get feedback.

Take the advice you see above. This just happened to me with a Music Hall Maven that I use in a room just for TV sound. I was planning to give it to Goodwill, but just for fun I plugged it back in, and guess what? It worked fine!

Try unplugging your Nad for a few minutes. Plug it back in and see if that solves the problem.

That's a common fix for personal computers which can take several hours to completely discharge the power supply. I would recommend when it is unplugged turn the power switch on and off a couple of times. That will discharge the power supply almost instantly. That said if that temporarily resolves the issue and it keeps coming back you may have a problem with a power supply voltage regulator.

Try unplugging your Nad for a few minutes. Plug it back in and see if that solves the problem.

That may be some type of protection. If you try to turn the volume up too fast, the unit may be programed to think it may be an accident, and is set up to not harm your speakers. I think I remember reading about a feature like that, but to be honest, I don't recall if it was NAD, or some other brand.

That's one sweet amp you have there! I believe the volume control is micro-processor controlled. If you haven't already try powering down the M3 completely (not standby by mode). It may be the processors in the amp need to be reset and powering down would do that.

Cheers,

Scott