Just like the old study screen, MathJax looks ugly for some expressions in the new study screen. Looks fine in Anki Desktop.
<anki-mathjax block="true">\sqrt{\frac{p(1-p)}{n}}</anki-mathjax>
Anki:
AnkiDroid:
Look at the square-root symbol.
AnkiDroid 2.24.0alpha3 with new study screen enabled