Back in January, when I tested the same browser on an entry-level Nokia Windows Phone, it worked fine on both the cellular network and on my Wi-Fi network.
The first is WebGL, which provides a way for web developers to access the low-level graphic capabilities of the computer or device that the browser is running on.
This existing vulnerability was the driving factor behind the above modifications as browser-based crypto is not seen as sufficient protection from determined State-level actors.