I just found this thread. I have been having issues for months as well. it started on Websites and would only find certain items if I put a debugging pause, then right-clicked on that step and chose "Highlight on screen." It would highlight, and then if I resumed the test it would work fine (unless it got to another item it didn't like).
15.71 was the only version that worked. I put in a ticket.
15.76 fixed the website issue for us, but now our Windows app is broken and doing the same thing. I let them know in the ticket but they said it is a different issue now, so I need a new ticket.
So I put one in last week, but not much has happened with it yet.
Now with the Chrome/Edge update breaking all of the web tests, we are going to need to update to 15.77 to fix those and I am assuming our Windows apps are going to break again.
Not fun.
