I have been having issues in the later versions of WAB developer in particular with the widget icons in the header controller appearing for an instance when the app is first loads (or reloads), then disappearing. Sometime they re-appear again after a second, but most of the time they just vanish. I can get them to re-appear by adjusting the size of the developer tools window. Also, this only seems to be a problem 'only' after I export the application to a zipped file, then extract and re-open on our server. I am wandering if this could be a resolution issue, since for some reason 'after' I export the app, the appearance changes and the resolution is higher. I know this because the header controller appears 'thinner' despite the fact that the pixel height has not changed. The same goes for the width. After exporting the app, the pixel width of the header controller is much higher, from 1398 to 1748.
I came up with a so-so fix, but I am hoping someone has had a similar experience and may know of something I am missing. My solution for now was to change the calculation in the header controller widget.js file on line 664 from:
var containerWidth = box.w - headSectionWidth - this._getEmptyWidth(box);
var containerWidth = box.w - headSectionWidth - (this._getEmptyWidth(box) * 1.1);
This decreases the container width slightly since the current calculation seems to make the container too wide, forcing it down (along with the icons)