I got fed up with my HH5's WiFi falling over at least once a week and needing the hub rebooted to work again. (5Ghz fails first, then 2.4Ghz plays up). From what I can tell, it's a common problem and unlikely to ever be fixed.
Solution? .... Get a BT Whole Home Mini system, currently around £75 for the 3-disc pack. It functions as a wireless AP that you can use to replace your HH5's built-in wireless AP. Just set them up and turn off your wireless networks on the HH5. Easier and cheaper than trying to source a replacement modem/router for the HH5.
It has been rock solid for me for the last month. No dropped connections, no need to reboot anything and excellent WiFi coverage in all areas of my house and into the outdoor areas too.
If you should change your router/Hub in the future, you can continue to use it with whatever the new hardware is, it is a replacement for Hub wifi but plugs into the Hub via ethernet.