Duplicate of UE-4695
In any multi-line text field, scrolling to the end of the last line with the control+right (skip word) command will freeze the editor.
In the AnswerHub thread, user twiddle linked to a Pull Request he submitted, where he claims that FString.Len() trims the terminating character, causing IsAtEndOfLine/IsAtEndOfDocument to be incorrect, which results in ScanForWordBoundary looping indefinitely.
1: Open any project.
2: In the Content Browser, create a new Widget (New/Create->User Interface->Widget Blueprint) and open it.
3: In the Widget Blueprint, add a Multi-Line Text Field (type Multi in the Palette and drag a Multi-Line Text Field into the blueprint).
4: In the details panel of the Multi-Line Text Field, type a word (I used the word "hello").
5: Place the cursor at the beginning of the line (before the word), then enter Ctrl+Right to skip to the end of the word.
6: Observe that the engine is no longer functioning.
Head over to the existingAnswerHub thread and let us know what's up.