Zotero has started randomly highlighting records in dark grey, see example image below. I did not select this record (if I deliberately highlight a record it's blue as per the image), and I can't find a way to get rid of the highlight, except restarting Zotero. Everything still functions, but I'm having to work around this apparently irremovable grey highlight. Switching to another collection and back does not clear it. If I restart Zotero, within a few minutes the issue happens again, on a different record.

I have no plugins installed.

I updated to 9.0.6 just now, hoping that would stop the issue, but it's still occurring.

Have I accidently triggered a programme feature I was ignorant of? Or is it a corruption, or a bug? I hope it's just a user issue, as it's hugely distracting to the workflow.

https://s3.amazonaws.com/zotero.org/images/forums/u21176302/0sw61423z9i3vamckbim.jpg