Diacritics and characters not displaying correctly in certain labels

We are experiencing an issue with the way some of our languages are displaying in the topics sidebar, progress indicator and other areas of Rise. Characters and diacritics are displaying correctly within the headings and body text using Open Sans but text with the default label font is no longer displaying correctly. We have issues with Greek, Romanian and Czech so far. The editable label text area shows the labels correctly but not in the course edit or preview. Images attached. 

This seems to be something where the appearance has changed recently as we did not have this problem previously. Has there been an update to the default fonts used for these items that no longer support these languages? Is there a way to fix this?

We can not release any of our courses with this display issue.