Several days ago I found out that strange non-transpaent white bar had bacame visible on Develop mode. It stucked on the upper part of the picture and I did not find any way to hide it. There are two users on my MacBook. If we use Lightroom under the second OS user, the bar is only visible on the upper-rigt corner of develop window not blocking the upper part of the photo like shown below.
Screenshot #1. Blocking file info bar
Screenshot #2. The second OS uder. The bar is on the upper rigt corner.