Underline the line above selected one

When I select a text and click underline or highlight in ipad, the underline/highlighted function happens to one line above the selected line. Happens only in 1file which is a big 3000 page textbook. Started to happen recently. Earlier I have underlines 100s of pages of same file same in ipad itself. I don't want to loose those. 

And this happens in ipad only. When i transfer this file to Android phone this error Durant happen. But it repeats in ipad when I transfer it back from the Android phone. Please help me.

Version is 20.04.00 (20200410.112051). 

Thank you