ofxFontStash blocky when android unlocked

If I create a simple android app the draws some text to the screen using ofxFontStash it works fine. But, if I then lock my android device and unlock it, the text becomes blocky and unreadable, like here: https://github.com/openframeworks/openFrameworks/issues/2028

Possibly it’s the same issue but I’m not calling ofEnableSmoothing anywhere.

Any ideas?