The Base CSS endpoint seems to no longer return all the necessary CSS that's used by the app.
https://en.wikipedia.org/api/rest_v1/data/css/mobile/base
The following output from the endpoint is indicative of the breakage:
/* Problematic modules: {"skins.minerva.base.reset":"missing"} */
This is resulting in various incorrect styles applied to our article presentation, including but not limited to: