Dancing letters after exporting to jpeg/png

Hi guys,

I am setting a text in Suisse Works Medium and I have stumbled across the problem that the letters in the exported jpeg or png seem to dance up and down, regardless of the antialiasing or compression setting. However, when I outline the text, it comes out nice and straight.

Interestingly, this problem only shows up on smaller font sizes - the example is set in 9mm - with the regular editable text above and the outlined text below. See attached, using a dummy text.

Any ideas as to what might be causing this?

Thanks