On the following screenshot, the sum of the image height and the bottom wrap margin is not divisible without remainder with the page baseline grid, thus the top edge of the frame below the image is misaligned - and because of that the test of the text in that frame.

To avoid it, the image height has to fit to the page baseline grid, and the bottom margin must be equal to the page baseline grid.

See also Enable/disable lock to the page baseline grid in Fred4 and Aligning objects to a baseline grid.