It is a new problem for Hebrew Wikipedia that started with the Typography Refresh in Vector.
To have a better interface and design.
(I'm using the vector). At each zoom the text changes. In headers text changes are irregular. In one zoom they are smaller than content or resemble content text. Here are some screenshots:
h4 smaller then body text (content) - zoom lose of proportion.
h3 seems like bold body text (content) - zoom lose of proportion.
Pics text as body text, side bar buttons bit smaller. Compare to next zoom to see loss of proportion
Pics text and side bar buttons are extra small, body text almost didn't change - compare to previous zoom to see loss of proportion (Zoom1-pics text size and side bar text size - new-vers).