Newer routers from Asus, Netgear, Cisco, Ubiquiti, and others have an option called Airtime Fairness or Wi-Fi Multi-Media (WMM), which can cause low bandwidth devices like Guardian to fall off the network or show as non-responsive in the app.
Please login to your wireless router settings and DISABLE Airtime Fairness and/or WMM this will create the best environment for your Guardian.
In your router settings it is usually under:
Wireless>Professional>Airtime Fairness > Set to Disabled
An article on what it is https://routerguide.net/airtime-fairness-on-or-off/
You can also disable 20/40 MHz Coexistence on Orbi routers.
For Orbi routers you can find the setting here: