New Xfinity Router dropping Wifi

Hello, I was receiving texts about Xfinity router being old (although we had no problems with it) and so I traded it in for a new XB6.

Even though the app claims our signal is 119%, this new router is constantly dropping us from our own network (devices: two phones, two desktops, and a tablet) telling our phones "unable to join ... this network is operating on wifi channels in use by several other networks" and on my desktop sending pop-ups telling me to find hotspots instead of my network (my desktop computer is next to the router). 

I logged in to admin 10.0.0.1 and can see that the 5g is disabled and that the 2.4g is set for channel 11 and channel range for 20. When I try to enable 5g and/or set 2.4g to 20/40 range and save it, it reverts to deactivating 5g and to 2.4g with shorter 20 range. Also, weirdly, we have two smart bulbs that I understood would not connect to the dual band, but even though there is no working 5g, they will not connect to this 2.4g now either, even when we manage to get our devices on the network. 

What are we doing incorrectly, or is it a bad router? At this point I am unclear what I am paying for with no 5g option and a janky 2.4g with no range.

Thank you in advance.