Hello there
Have same problem with a Connect Box received about one month ago: both Apple and Android devices work over Wi-Fi for from few to several minutes only, then the connection is broken, only switching Wi-Fi on the device off and then on helps.
Have restarted Connect Box several times with no positive changes.
Yes, LAN was not affected.
Workaround: disable 5 GHz in the Connect Box (192.168.0.1 -> Advanced settings -> Wireless -> Wireless signal, click on Disable 5 GHz).
Now everything “flies”, yes, at a price of the reduced Wi-Fi speed.
So it looks as if in the new Connect Box something would be wrong with the 802.11ac.