WNDR 3800 - Trouble with Chromecast & Wireless Printer

Hello all,

I have a WNDR 3800 that has been giving me fits for awhile now when it comes to two things:

1) Chromecast - My chromecast has already been setup, but phone just won't discover the chromecast.

2) HP Officejet Pro 8600 - Same issue as the chromecast - The printer was already setup, but my computer won't print to it through the netgear wireless network like its supposed to.

Here's the kicker:  After many google searches I tried turning off the UPnP setting within the Genie program.  This did the trick!  Both the chromecast and printer worked when need.  Then a week passes, and nothing works again!  I go back into Genie, turn UPnP on, and everything works again!  For a week...then I go in and, for the hell of it, turn off the 5ghz band (since we don't even use it), and both the chromecast and printer work again seamlessly!  

In summary, its almost like I need to "wake-up" my router by changing a setting, ANY setting, so it recognizes the chromecast and printer, which I'm communicating to from another device on the network.  I'm confident its a router issue, and the same thing is plaguing both instances.  Why can't my devices communicate to each other through the network without changing a seemingly unrelated setting each time to "wake up" the router?  Has anyone else had this issue, and how can I fix it permanently?