I am having same issues with widgets and actual map loading in WAB 1.2 developer while editing map. It is slow and needing constant refreshing. Once map deployed to server it seems fine. One particular widget that is not working under WAB 1.2 is the draw widget that requires restarting the browser numerous times.
The launch pad theme is a great looking theme but it has serious issues right now. It does not fire the onClose widget event (and possibly the onOpen either). Widget that depend on this events to do things like deactivate the draw box and clear graphics suffer from these events not being fired.
I have been testing other themes and seen that the Tab Theme also has issues. The results from the Graph widget do not get removed when you close the widget until another widget is used. The google street view peg man stays on the map even when the street view widget is closed.
Which/Whos Street View widget are you using? I just tested my Google Street View Widget 1.2 - 8/25/15 using the tab theme and the street view peg man is removed when the widget is closed/minimized.
I don't know why I couldn't get this to work but your link and download worked. Thanks. I still have an issue that WAB developer 1.2 loads but freezes and needs numerous refreshes in edit mode before I can do anything like add a widget or turn off/on layers. It seems the communication with my Server map services is much slower, hopefully just a network issue on my side.