I live in a new multi story house, and we have bad reception in the elevator and lobby area. When standing right next to the door, we get some reception, but otherwise there is none. Tapping the unlock button in the app takes some time to react - can take up to a minute. Using the Siri shortcut usually works immediately.
Same with the watch - very often unresponsive in our conditions, though in the case of the watch, I’m not sure if it has a bluetooth connect option.
Please test your app in low connectivity conditions. I guess the web option is attempted before the bluetooth option, and the timeout is too long, or something like that. It would also be great to make the watch app work without reception.