command shift 5 box frozen

You may be able to deal with this without restarting.

When the problem occurs, open Activity Monitor (or have already open in the background if you anticipate that it may occur).

Type, for example, the word screen in the search box:

Select Screen Shot and click the Stop button in the toolbar above it.

This, however, just deals with the symptoms, so we can still work towards a cure.

Please test in Safe Mode, and also create a new user account, or activate the Guest access, to test.

This will help us to determine whether the problem is specific to your account, and whether it is likely caused by interference with some third party software.

There is a chance that the preferences file for this has gotten corrupted somehow.

Paste the following line in Terminal, and then copy and paste the output here:

defaults read com.apple.screencapture

Try the x in the image below and / or the previous Posters' suggestion " esc " Key on Keyboard

What white box? Are you referring to the image that P Phillips showed?

As seen in there, after choosing one of those options, click on the actual word “Capture”. Are you saying that it doesn’t go away after that?

Have you pressed escape, esc?

Does this persist after restarting your mac? Does the same problem occur of you start in Safe Mode? Does it occur in a different user account?