Hmmm... odd... I would have to go back to some app is conflicting with this, I bounce between half-dozen different WiFi networks a day on two sets. I am a IT tech and deal with networks all the time and I never have to do anything but let my Rezounds connect and go. In my network "lab" we have several WiFi networks on different hardware running with varying encryption and type all the time and my Rez switches between them flawlessly. I have used them flawlessly with Meraki, Ruckus, Cisco, HP Procurve, Netgear, Linksys, Sonicwall, EnGenius, D-Link, and a host of other APs and wireless routers with no issues what so ever switching between them and back and forth to 4G with either of my phones, one of them is bone stock, has most non-essential apps disables, and less than 10 apps installed for work from the Play Store, the other is my personal Rez (currently stock and rooted) with a ton of assorted junk installed.
My first suggest would be to make sure you are on the latest software, 4.5.605.14, and if that is correct you should factory default your device, especially if you haven't done it over the last couple updates to the Rez. HTC typically has some of the best implementation in radios, both Mobile Network and WiFi, the issues you state above are not normal.
If you do have a WiFi issue with your HOME router, it is most likely a configuration issue or your router manufacturer has done something non-standard in their implementation. I would default the router, change the mode to disable 802.11b (so G-Only, G/N-Only, or G/N/AC only) and WPA2 Auto with a reasonable mixed case&type key of 8-12 characters, and a SSID that is under 12 characters and does not contain special characters or spaces and all should be well on newer routers. If you are using a 802.11b router only, get a new one.
