There could be a way.
I updated from stable to 16-Jan snapshot and there were some problems (network configuration changed), but I finally solved the situation using the reset button.
See Reset button problem in 19.07.1 on BT Home Hub 5A
I used the first method: Holding reset down while powering up until the LED starts flashing (green on this device) and the device goes into failsafe mode (with rapid red LED flashing on this device).
You can try to use firstboot & reboot now commands or you can even send a previous version of openwrt via SCP and perform another upgrade.
Give it a try & good luck.
Sorry for not being contributing to the speed test, but my Internet connection is 100mb, so I cannot see any difference.