IME input is ignored when There are some lines in MultiLineEditBox

This problem is reproduced on other widgets using MultiLineEditBox.
ex.) description in source control commit log pane, comments in blueprints, etc.

1. Place a TextRenderActor in the level
2. Select the TextRenderActor
3. Put some Japanese characters in Text property (this is MultiLineEditBox)in detail pane
4. copy the line (Ctrl+C)
5. Paste the text multiple times (5+ times)
6. Try to input Japanese characters in the MultiLineEditBox

Result

Japanese characters will not be added to the text box

note

• If Japanese IME is disabled, text input is not a problem.
• Japanese characters can be inserted at some lines from beginning of the text box (see attached video)