I have experience with one Doorbird. Key to stability was using Ethernet network interface and not Wi-Fi.

If you can't homerun Ethernet back to the router/switch, use a mesh Wi-Fi solution like Eero running in bridge mode. Locate one unit near the Doorbird and connect the Doorbird to the Ethernet port. The Eero mesh is very reliable and will provide a network connection that doesn't drop out intermittently like a weak Wi-Fi or older Wi-Fi extenders.

Only drawback is that Eero doesn't have PoE so you will have to power the DoorBird with a separate power supply.