Leave the bulb on power while you take the hub off power.
We should also note that even if the bulb is acting as a repeater, you might still have the problems with the arrival sensor doing the home/away/home/away pattern due to Wi-Fi interference. I have this particular problem at my own house. But that’s a topic for an entirely different thread.
Back to this thread: anytime you physically move a device to a new position or add a new device to the network you need to rebuild the neighbor tables for each device or they won’t know who their true neighbors are (and won’t use the new repeater even if it’s right next to them).
For zigbee devices, you force a network heal by taking The hub off power (including taking out batteries if it has them) for at least 15 minutes. When it comes back onto power, all the other devices will begin rebuilding their neighbor tables. This can take a few hours, so you may not see the results until the next day.