Communications error (error 105) when trying to update firmware

The Bond hub works perfectly with both HomeKit and Home Assistant, but I am unable to update the firmware from 4.37.30-beta to 4.37.40-beta or 4.37.40 (stable)

The upgrade progress never goes about 0% and eventually (after about 30 seconds) it returns this error:
There was a communication issue (error 105)
We couldn't connect to your device. It might be performing a firmware update. Please make sure you have a stable internet connection and try again in a few minutes.

I have rebooted the wifi, the bond hub, checked channels and DNS servers. everything appears to work with no issues - except the firmware update.

Anyone have any ideas?