This happens to us as well sometimes, especially when dealing with links. We find if you copy your content in and then paste it again without the formatting (Ctrl Shift V) and then relinking things if you need to, this tends to fix the issue. We're not sure why it happens but we think maybe when we've copied and pasted stuff.

KB doesn't show a difference between the fonts in the edit view, but it makes a HUGE difference in the published view. When viewing the text in edit, Arial is the font, when but publishing, it shows up as Oswald.

screenshot 1: When the edit shows "Font", the text publishes as "Oswald"

screenshot 2: I change it to "Arial", and visually nothing happened here

screenshot 3: but when it's published/in draft, here's what it looks like. See the difference in the word "bankruptcy"?

I've seen this too but (for me) it's not been a problem with HJ, but rather with source formatting. This especially happens if you're pasting in Word docs. Have you viewed the articles in code view? Try that and see if there's any HTML/CSS junk in those smaller-font instances.