The only thing we can suggest is to check each of the connections to the instrument including power and any pedals, controllers or external device connections.

Did you ever get your the problem in your other thread solved? If so it might help others if you update that thread with your solution.

Maybe a polyphony limit reached and you had to wait for sustain to run to the end of the sample?

If you're leaving the sustain pedal pressed without lifting up then you can, theoretically, run out of polyphony resources.   

Just throwing an alternative idea log on the fire.

What preset piano patch were you playing?

How were you playing it? Lots of chords and notes at the same time?

Can you describe what you were doing when it happened?

Hi, if it's a polyphony issue like Jason write, you can check my tutorial video on that topic 

Understand the polyphony management for your MODX M, Montage M or ESP https://youtu.be/eiXoPeu-ElU

Like Pete write, providing more details will help.

It was a basic Piano preset, "CFX Concert" , I believe. there's no way it can be due to Polyphony since I played very basic chords wit h no more than 7 keys total. Piano pedal wasn't held for longer than usual just basic piano playing. 

MODX was connected to a computer with USB as it has been for past many months since I bought it when it came out, nothing was running on the computer besides google chrome and UA Apollo software.

The audio outputs were routed thru Apollo Interface 

Thanks for the additional info. Possibly there is a loose cable connection inside the case. There could also be a problem solder joint on one of the circuit boards. Those can cause intermittent problems due to heat or moisture.

Another possibility is that something fell into the case (dust, particles) or there is a loose nut that worked its way into a position where it caused the problem.

First thing to try would be to run all of the diagnostic tests.

1. Turn off the instrument

2. disconnect the usb/midi/pedals/other connections

3. Power up in Test Mode - hold down the C#2 chord (C#2, F2, G#2) on the keyboard while turning the power ON. Release the keys once the Yamaha logo appears on the screen.

There are some 39 different hardware tests for all of the buttons, knobs, sliders and lights. 

You could try unplugging the modx m and shaking it GENTLY (emphasis on gently) while you turn it in various positions while listening for any sounds like a loose screw or nut. Turn it upside down while gently shaking to see if anything falls out.

Unfortunately there is little else you can do unless you want to open the case yourself and look around. Probably not a good idea for such a new instrument.

You would need to take it to a service center for them to open it up and do checks. 

Just to isolate things, I would unplug the USB port and only use the headphone output.  No sustain pedal plugged in. This would remove the possibility of MIDI loops and sustain interaction.  Not that I suspect this is the case but it's always best to start with minimal configuration that can have no holes poked in it as possible sources of issues.

If there's some kind of issue with your keyboard then I would expect the problem to persist.

If the problem can't be reproduced then I would hook up the main L/R output (not USB yet) as a next step and see if the problem is isolated only to this output.

If the problem still can't be reproduced then I would add the sustain pedal back and try again.   

If the problem still can't be reproduced then I would suspect something isn't setup correctly with USB since adding USB will certainly cause the problem to resurface.

Hi folks. I made an account just to reply here and report that I've been experiencing a similar problem. I just bought a brand new MODX M8 a few days ago and have also gotten strange pauses in the sound for 2-3 seconds just to have it all come back right after. It's as though the notes I play get buffered for 2-3 seconds and then all get played at once after that short pause. I've also been getting notes held for too long even after releasing the sustain pedal, which is a different issue but with a potentially related root cause. I've been using the basic piano performances CFX Concert and C7 Grand. These issues are difficult to reproduce, which is very frustrating. 

I'm going to power up in Test Mode and run those diagnostic tests mentioned by Pete and see what comes back. 

Thanks for providing info about your experience.

These issues are difficult to reproduce, which is very frustrating.

Exactly - intermittent problems are some of the hardest to try to diagnose. When we can't reproduce an issue there aren't any clues to know just where to look.

If you are still on warranty you might consider the service center route. They will have the same issue trying to find 'the ghost in the machine' but at least they can open it up and check all of the connections.

We always advise being as proactive as possible and providing the service folk with a lists of things you want them to check. That list might include:

1. please check all internal cable connections by unplugging each one, checking the connections on the cable and board for corrosion or damage

2. look for any signs of moisture, water damage, discolorations, dust or other foreign objects

3. check all circuit boards for cracks and to make sure they are securely connected

A good service team will do all of that on their own. But by providing them a list like that they are obligated to document in their service report to you that they actually checked those items.

You paid a lot of money for your instrument so you are entitled to know EXACTLY what their evaluation involved rather than just a general statement like 'we thoroughly examined the inside and found nothing'.

I booted into test mode and all the tests passed. However, I did notice that the board is running firmware version 1.00.2, which seems to be a bit behind the times, as I see that MODX M firmware updates up to 3.00 are out. I plan to perform this firmware update. Hopefully that fixes my problems. If that doesn't fix it, I'll consider the service team route. 

Thanks for the update. Although the older OS version isn't likely to be the root cause your idea to update to the latest OS is a good one. With an older OS it's too easy for a service person to put the blame there without doing a thorough check.

And in our experience with polyphony issues there are just dropped notes - not dead silence for even a short period of time. Don't overlook the 'gentle' shake and listen test to see if you can hear anything loose.

Haven't looked inside a Modx M but we have heard that the keys are manufactured in blocks of 3-6 rather than having individual keys. So if a block, or the circuit board related to it, goes bad it can affect more than one key.

Keep us posted if you find out anything. 

If you record MIDI every time you play then you can take a look at the MIDI data to see if the problem is that there's no 'note on" events causing the dropout or there are note on events and nothing responds to them.  Plus you'll have something to play back that would demonstrate the issue and to give to others.