d to baseline grid' but it's not in line with the first line on the left page, strangely. I've tried inserting text tool at beginning of (red) line and deleting to take it back to the end of the previous (top) line, then soft returning, which gets the line spacing correct, then I have to type 5 character spaces to get the first word to indent the same as the other paras. BUT another weird line space will appear further down the page. I've checked the leading, it looks fine. I've tried deleting a few words at the end and beginning of the two sentences either side of the problem, and retyping to try to delete any weird breaks, but the problem persists. And as I say, if I manage with a soft return to remove it, it will appear lower down the page. AAARgh!
If you look at the tops of the columns on the two pages you'll see that the the text is not aligned the same. I would guess that your text frame options are set to have the first baseline aligned to ascenders, but you really want it set to leading, or you want to change you align to grid setting from first line to all lines. In the left column the text starts lower because the first line is aligned to the grid. There is some space before the red text (maybe just a hard return combined with the Align first line to grid) that is created when the first line of the red paragraph is shifting down to align to the grid. It appears to be aligned with the second line of the paragraph in the left column.
Thank you. I aligned all to grid, the problem is solved.