Font Displays for Pīnyīn

I have noticed that when I write in pīnyīn, the “ǔ” diacritic, indicating the third tone in Mandarin Chinese, sometimes appears in a different font than the rest of the text (it is particularly noticeable when the third-tone diacritic in on an “a” in italics.

Has anyone else noticed this? Do you think it is an issue with my web browser?

Downloading font files takes bandwidth, so, even though our font, Skolar, has an extremely large character set, we subset it for the glyphs we use commonly. Any glyphs outside this range will show in a different font.