When text is flowed into a linked frame on the next page, its font size is inexplicably tiny at the top of the next frame. I have seen the same thing happen but with a huge text size, and also wild alternation between huge and tiny as the text is reflowed between the frames. This problem occurs seemingly randomly.
Regardless of how much I have fiddled with text style resets and overrides, I cannot find a lasting solution - the problem recurs. The only solution has been to rebuild the document from scratch in a new file.
I suspect this bug may be related to IDML import, as to date I have only seen it happen in documents I've transferred from InDesign.