Yamaha service. Depending on when you bought it - there was a warranty extension at one point. Make sure you're not covered by warranty first before getting the hoover out.

Hi Montage masters...Iʻve recently started having problems with the Middle C playing intermittently. I started looking around and found its a common issue with Yamaha Keyboards. Some people suggest removing the Keys and vacuming dust...anyone have a suggestion? I have already backed up everything did a memory reset. I am already in the newest version of firmware.

Is it the key itself? That may initially sound like a strange question, but I ask for this reason: do the missing notes also occur when you play a .mid File, or Arpeggiator?

If the key mechanism is broken the note will sound flawlessly via these other sources... and you likely have a broken key mechanism. Those who break keys, will usually find they break keys. Others never have that issue... mileage varies, as you can imagine.

If the note continues to be intermittent under MIDI or Arp triggering, then you likely have 1) an operator error (not uncommon) or 2) a very sick instrument. To help eliminate the former, please recall a specific program and report on the situation under which you are playing it.

Again the reason... we hear from folks who are unaware of how Note Limits and Velocity Limits work. It is possible for notes to appear intermittent. They conclude that notes are intermittent when actually they are behaving absolutely as programmed. Example, if you copy or recall just Part 1 of the “CFX Concert” Performance, you may conclude that the sound is intermittent when that is NOT the case at all. Part 1 when recalled by itself will only respond to Velocities between 2-92...

Some people can play this for an hour and never realize that when they exceed 93 nothing sounds... believe it or not they never or rarely exceed that Velocity Limit.
Some conclude its certain notes that are not sounding, others claim it comes and goes randomly... mysteriously...
What actually is happening is they recalled just one Part of a multiple Part program... and this one Part only reproduces sound when Velocity is between 2 and 92... without Part 2 present, Part 1 does not play at all Velocities

This may or may not be your problem, but because the instrument can appear to have issues when it, in fact, is behaving as it should... we’d be remiss if we didn’t point out this all too common user error.

Try the “Init Normal (AWM2)” does it play or sound intermittently?
Let us know.