Highlighting Problems in PDF Files on iPad after the recent update

I use my iPad for school - reading and highlighting important things in the PDF file.

It worked well in the last semester.

But after I updated the iOS on my iPad in recent, the highlighted lines keep moving up or down and to the right in the file. All the highlights in files are being misplaced and sometimes even covering other sentences. It just line whole layer of the drawing lines shifted away.

Similar things happened 3 times in this week. I removed the wrong highlights and re-do in the correct place; it wasted a lot of my studying time! Now another files get this same issue… is there any way to fix it? I really don’t want this happen again!

[Re-Titled by Moderator]