Let’s see if I can help out a bit…I have EXACTLY the same router as you, so here are my thoughts:
Do you have different SSIDs for the 2.4 GHz and 5 GHz radios? IF you have the same name for both THAT’S probably the problem! Even worse if you have that “Smart Connect” option enabled. My first guess is the Bond is getting confused there.
I have different SSIDs and I use an older phone dedicated to 2.4 GHz which I used to re-add the Bond and back up my settings yesterday. I also use this phone for adding/updating any other devices which only have a 2.4 GHz radio. I sort of ran into this problem yesterday when I rescue reset my Bond, and couldn’t re-add it with my main tablet which I ONLY connect to my 5 GHz radio. Even though I saw the name of my 2.4 GHz network, I could not re-add my Bond without being connected to it. ONE SSID would REALLY confuse things!
Summing this up, MAKE sure the device you’re using is connected to 2.4 GHz, maybe even create a 2.4 GHz Guest Network dedicated to IOT devices, then try to update. If you wanted to keep the same SSID, I guess you could try temporarily turning off the 5 GHz radio, then try to update.