Some of our users are reporting an intermittent issue where all map text is corrupted or missing. This is affects both rendered labels and lines.
It looks like the Font->glyph map isn't aligning or has a DPI mismatch?
The font in the screenshot was "DIN Pro Medium". Restarting the app fixes the issue. We've observed the issue on both Android and iOS, (Screenshot is IOS):
IOS:

Mapbox Studio
