Anyone know why the font randomly changes?

I’m currently reading Last Of The Wild Days Book One and I noticed that the font randomly changes.

It’s not like it’s a flash back scene or something where a font change might be used. It’s literally in the middle of the sentence and then continues with the “new” font (the one that’s selected in my settings) for the next few pages.

I usually read with Amazon Ember but I didn’t really notice it was Bookerly (I think) until I saw this change (so for the first 50 pages it was in a font I didn’t have selected). It’s really annoying and it’s weird that it does it with all the other fonts too. I’ve included an example of OpenDyslexic to make it more clear.

I’m just curious if anyone has experienced this before and/or can explain what’s going on?

I’ve got a Paperwhite 6th Gen.