Oswald not rendering in Firefox and Chromium on Linux

It has been a few weeks now that the Oswald font does not render anymore neither in Firefox nor Chromium on Linux (Debian 9.5). It works fine on Windows (both with Firefox and Chrome).

A related [Stackoverflow post](https://stackoverflow.com/questions/56446781/why-google-font-oswald-is-not-displayed-in-firefox-and-chrome-but-is-in-other-we) exists, but it seems no issue has been opened yet.

As described in the Stackoverflow post, if you go to https://fonts.google.com/specimen/Oswald, the text shows up briefly then disappears.

Looking in the Network -> Font page in the Chromium inspector, 5 Oswald fonts are queried (https://fonts.gstatic.com/s/oswald/v23/...) and return 200. All but one show an actual font in the preview tab. https://fonts.gstatic.com/s/oswald/v23/TK3iWkUHHAIjg752GT8G.woff2 shows nothing in the preview, although the status is 200. The 4 other Oswald fonts seem to show a default font in the preview, not the actual Oswald font. Clearing Chromium cache doesn't change anything.

In Chrome on Windows, I get the exact same 5 fonts queries, and the one missing on Linux shows up on Windows, showing the actual Oswald font in the preview tab.