The problem is that the font does not have these characters. It has the glyphs, but they're encoded at U+0162 and U+0163, not U+021A and U+021B where you are probably expecting them (or more likely where your keyboard driver is expecting them). What you're seeing is the result of a font fallback mechanism, trying to display something for the characters. It works, but it looks horrible as you've pointed out.
Ask the font developer to update the font, properly encode the glyphs at U+021A and U+021B.