It may happen due to font cache corruption or invalid/broken font.
Even if you select "Ignore fonts mentioned in SSA", MX Player will still cache the fonts.
goto settings » general & clear the font cache if the problem persists.
There's a bug that the battery will tint with "Pixel blue" when it's under 15%. Here's why (framework-res.apk):
Left: Pixel Experience, Right: Pixel