This is a regression. Tested in //UE5/Release-5.0 CL20979098
Preview Mesh does not disappear after releasing the Keyboard Shortcut as expected. The Mesh remains until the editor is restarted or another menu is opened as a tab like the Editor Preference.
Expected Results:
The preview mesh disappears.
Actual Results:
The preview mesh remains and will continue to appear under the mouse.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-169712 in the post.