Had you upgraded to 3.5 at some point, perhaps even recently?

If so, did you do a complete re-initialization?

fwiw when I updated from 3.0 to 3.5, I didn't re-initialize and reload my backup at first. Then while exploring the new presets I noticed some unusual behaviour, namely UI slowdowns/freezes. After re-initializing this went away.

UPDATE: Red herring alert!

The error message displayed made me ultra-sensitive to any anomalies with the instrument. I rushed to report something here, as I said, before having gone through a complete set of steps to narrow down what the issue is. The normal "1, 2, 3" when you have this sort of thing happen.

I'm leaving my message unedited to help inform how things are not always as assumed - and it's important to get back to basics when something goes wrong.

After a long vacation - I wasn't ready to setup my Montage properly. Motor memory failed me and so my instrument was improperly connected to my studio's mixer/audio interface. This made everything sound completely wrong. Strange thing is that some waveforms sounded fine - like some strings. But lots of other sounds just sounded like different waveforms altogether. When I checked my clap was a snare (an electronic drum kit) - I thought that was wrong. Reinforced by what I was hearing (completely wrong) - I assumed that was the end of the story. Not so.

The electronic drum as a snare sounds like a clap. So that was not incorrect. And, come to find out, everything else (and I mean everything) is fine.

While in the studio the back of my Montage cannot be seen. And the ports are not labeled on the top of the chassis forcing either to remember the jack positions - or remind yourself by looking at the back of the keyboard. Neither of those things happened here - so I plugged in the instrument incorrectly.

Feeling from the back - I felt two jacks on the far left (looking at the keyboard from the front). Those are A/D inputs. Then I felt the next two jacks and incorrectly thought these were Main L/R. That's not right. Phones is actually between A/D In and Main outs. So that was it. Plug in a TS cable into your phones and listen to that out your reinforcement - it's going to sound wrong -- because it is.

Now that that is sorted - I'm back in business. No backup necessary. Time to make another backup - "just because".

The “please reboot to maintain internal memory” Error Message, as I understand it, is refers to the type of memory used in the current crop of Yamaha products. NAND memory, is a type of memory that meets the high speed access and large data size requirements used in the current round of Yamaha Synths and Keyboard products.

“Errors in NAND Flash can be classified into two categories: permanent (non-correctable) errors and temporary (correctable) errors. Memory wear is the permanent error in NAND Flash. Temporary errors in NAND Flash are Program Disturb, Read Disturb, Over-programming and Retention errors.”

The correctable error can be resolved by simply rebooting the system.
NAND is actually volatile memory because eventually the data will completely disappear or become corrupted and unusable. Typically, this happens with 100,000 rewrites (or, in other words, longer than you are likely to own the instrument). So for uses like in the synthesizer it functions as ‘non-volatile’ memory.

This “memory wear” is a fatal, non-correctable error, which can be resolved by replacing the memory and restoring your data from a BACKUP FILE. (That should not happen any time soon expected life cycle in use is ten years).

The error you are seeing — “Please reboot to maintain internal memory” — is the correctable type of error, where all you need do is simply reboot your instrument. I have never seen data changed by this... my guess is it is looking to refresh the buffers (edit buff and the recall buffer... but I would have to ask engineering)

Nothing to worry about.

Memory wear is another reason why you may see 16GB worth of of parts supplying 8GB of usable storage. Over-provisioning allows for cells to "die" and the memory controller reassigns, as necessary, the memory locations to keep your data stored in valid (not dead) cells. This is what would allow for memory wear to, at least for a time, not present a fatal error.

Regardless, over time (with memory wear - if that's a property of memory used) you will wear the entire part out and run out of space. There should be some simple calculations to determine a reasonable use case and give the keyboard a reasonable amount of life. Backing up will not always allow for restore if there aren't enough "live" cells to spill the data into. At that point, it'll be a service event to swap out the memory parts if the keyboard is still worth it. That lifetime calculation should have, for most, ensured that by the time a part is worn out - "everyone" is moving on to something better.

Although expensive, having removable memory would have been a way to insure against this as well. Although memory technology has a way of moving on itself - which is the problem I'm sure Yamaha ran into chasing down parts for previous memory modules. Ultimately, the cost was probably not worth it given validated memory parts go EOL fairly quickly unless you get on the earliest tip of the production curve.

I'm not so worried now that I can't detect a Performance with corruption and it seems all is well. I'm not going to run through the entire system - but what's important to me seems fine. Backups mean I'm safe regardless. I do take my own medicine in that department.

Looking forward to continued reliability. So far, so good.

"Memory wear" isn't an issue in most applications, especially ones like the Montage/MODX where not a lot of writing takes place. 100,000 cycles is per cell/bit/block, not overall, and if Yamaha were smart they use wear leveling algorithms, or at least a file system that supports it in their synths, along with remapping of blocks that do eventually fail over time.

I've had devices with various amounts of flash/rewritable storage for years, even more, and haven't had any "wear out" yet. Not even a flash drive, SD card or SSD, but I'm not a heavy user of them either.

As for performances getting corrupted, if there is any sort of checksum in the data format, these things can be detected at least. If they use a file system within the flash, something like ext4, there's some amount of integrity checking at the file level too.

Backups are always important, and memory wear/corruption is probably one of the less likely causes of data loss in a Montage, compared to user error, theft or physical loss/damage.

If you're constantly loading samples, libraries, new firmware, and user banks into your synth you might reach a lifespan limit in 10 years or more. By the time this happens Yamaha will have released the next big thing and you'll be ready to upgrade anyway.