ever seen LR act like this?

[Steve Zeeeee]

LIbrary mode

Suddenly there are no panels or options or menus or anything.

No commands change the screen appearance.

Tab only expands the thumbnail space.  Not the first time.

A restart fixes this.

LR 2015.8

OSX 10.11.6

[99jon · Accepted solution]

It is a known issue although usually intermittent on some Mac OS computers; but usually running Sierra. You could follow the thread below for progress. A couple of work-arounds:

Press G to go back to the Library grid followed by D to get back to Develop.

Minimize your window and then click the LR dock icon to re-open.

https://feedback.photoshop.com/photoshop_family/topics/lightroom-2015-7-in-macos-sierra-bugs