Our default font doesn’t contain Cyrillic, so a fallback system font was used, causing the inconsistent font appearance.
If you change font option to “System”, the issue should be alleviated.
The issue was much worse before (see: Cyrillic alphabet (russian letters) renders with broken broken formatting - letters are spaced too wide). After the fix, Cyrillic characters uses a fallback system font, so they look much better, but still slightly different from the default font.