When I first used the software, I found that if I imported my own PDF (with annotations in it), the title of the corresponding paper would be partially highlighted in yellow in Zotero.
After using the software for a while, I realized that the highlights in the entry represent the reading hotspot areas/progress of the PDF. I hope the software can add relevant hints, as it really looks like a bug at first glance.
https://s3.amazonaws.com/zotero.org/images/forums/u16018266/hnqqjedkixmgupruhldz.png