Edge 840 seemingly random intermittent beeping

My Edge 840 seems like it's always making noise. It will intermittently beep, repeatedly, and it's driving me nuts.

  • Tones are off.
  • Key Tones are off.
  • There are no sensors moving into-or-out-of range - it happens in the middle of the woods, when the unit was turned on in the middle of the woods and the ride was started in the middle of the woods, so my other sensors/bikes are certainly not connecting/dropping.
  • This happens with just a single active sensor (HR) as well as with multiple (HR & Power & Radar)
  • There are no text pop ups or anything happening on the screen during these beeps
  • I do not think it is a sensor disconnect issue (see previous three bullets - when power or HR or radar does drop out, I get a pop up saying so)
  • This happens with no radar connected (so this is *not* someone coming up behind me or something, which of course would be shown with a graphic and wouldn't be a mystery anyway)
  • Eat/Drink reminders are off, as are time, distance, high traffic, etc.
  • There are no Strava segments nearby (and this happens with segments off)
  • These are not from climbs coming up (or at least there is no visual indication of it being from ClimbPro)
  • These are not coming from phone-associated notifications
  • This happens with no Route loaded, no navigation at all
  • This happens with no workout loaded or active (and I've actually never done one on the unit)
  • This is not a Jump Alert (though the beep might be the same) - if it is, jump detection is broken xDp
  • This seems like it happens usually more often when moving slowly, but has happened when just sitting still waiting for riders to catch up
  • This is not from auto-pause (unless it is auto-pausing with no visual feedback, and with auto-pause turned off)
  • This happens most often in the Mountain profile, but I can't find anything meaningfully different between that one and the others, so I don't know if it's the profile on the device, or just the situation I end up riding in that is triggering something. 
  • I have no ConnectIQ alerts or anything installed.
  • I'm on latest SW as of time of posting, 21.18
  • My friends and my wife don't want to ride with *BEEP* me *BEEP* any more because *BEEP* it's really *BEEP* disturbing to *BEEP* have to listen to *BEEP* this thing, and hard *BEEP* to have a conversation *BEEP*. I imagine the wildlife is also concerned/annoyed, as are hikers on nearby trails.

What am I missing? What else can beep, even with all Tones *off* and without any visual feedback? I've gone through the menus 10x now and I'm not seeing anything that seems like it would cause this. Send help!

*BEEP* :)