Sorry, you are having an issue with your MOXF. Strange behavior indeed. There are some things you can try to remedy this odd behavior. In troubleshooting this issue we have to start by looking for a potential cause of this illogical behavior. Some things we'll look at deal with information you have not mentioned. We can tell you that Reinstalling firmware would not change anything and just adds to your frustration. The firmware either installs properly - in which case it reports "Completed", or it fails entirely. We recommend making a Backup file of your current work, then resetting your instrument... Described below

When I’m playing a lead patch with with mono retriggering, my G key doesn’t retrigger from C. i.e.: I play a G, keep it held, and press C; but when I let go of C (still holding G) the G does not retrigger; instead, the C note just keeps sustaining. The problem also works the other way: C won’t retrigger from G.

The video shows you are in VOICE mode. The Voice you selected, "Huge Lead" has Portamento. This is a glide feature that that when you play legato (the gesture you describe as holding a note while fingering another key) the envelope will not retrigger on the second note, rather the pitch will slide to the next pitch. How long it takes to reach the second pitch is a programmable function. Things that can influence the behavior are the interval (the distance the pitch has to glide), the Portamento Time setting (how fast the distance is covered), and the other slope settings. Since the distance of the glide has bearing here, we wished you had played more of a variety of distances in your video or in your description. And we wished you had mentioned any other controllers or devices that might be involved, sustain pedal, computer, etc. These can influence your results.

You say it happens whether or not Portamento is ON or OFF. So this begs the questions: are you connected to a computer? What is the current condition of the Local Control parameter? What is the MIDI routing status of your instrument? Is a sustain pedal involved? Are any outside Control Change messages being applied simultaneously? Does a connection for passing said messages exist? If yes, disconnect it, and attempt your experiment again.

Did you try executing a FACTORY SET, to reset your instrument?

Save your data in an ALL data file (so you have a backup of your work... WARNING: a Factory Set will wipe out your User data), then perform the factory set (reset your instrument) this will cure the issue, if it does not, please take your instrument to an authorized Service Center. (Unless of course, there was some MIDI routing you did not mention... In which case we'd need to know what was connected at the time of the odd behavior). What occurs in your video is indicative of either a MIDI routing situation (log jam) or a unit that needs to be reset. Strange behavior can occur post an illogical routing situation. And only a reset will restore logic.

Press [UTILITY]
Press [JOB]
Press [ENTER]
Press [ENTER]

Let us know. If you need help locating a nearby service center tell us where your located.

Thanks, Bad Mister.

I've done a reset as you described. No external connections were involved. I was operating in standalone mode with no midi going in or out. Local control was on. Problem still persists on every monophonic patch, however.

Looks like it's time to call a service center... I'm working with a 1 year warranty, right? Please tell me it's longer! 🙂 looks like I'm just outside of that.

Sustain pedal?

Nope. No sustain pedal (or any other pedals). Nothing plugged in but the power cable and some headphones. And like I say, only two pairs of keys are affected. I should also note, that the thing is in perfect shape otherwise, and the behavior appears to have manifested out of nowhere... It worked fine, then I turned it off after a rehearsal (in our air conditioned space), didn't move it or anything, came back a few days later, turned it on, and it was doing this thing.