Using AFPUB 1.8.3, OS X 10.15.3.
Cosmetic?
Please see screenshot. The 4 text frames are linked for text flow. The images within all have wrap settings of "jump" with 3mm spacing. If you select all of the text in frame 1 with CTRL-A, the selected text is ghosted in the wrong places. You can see, for example, the bottom 2 text frames have "shadow" highlights that precisely match the actual text in shape, but are somehow shifted down below the actual text. This seems to be related to the size (spacing) of wrapped images and perhaps the flow link to a new spread/page as I have just started using the "wrap" feature and have never seen the problem before.
It's a cosmetic thing, I suspect, but the highlighted "shadow" boxes should be exactly overlaying the actual text.