Shift key makes the cursor go to the head of the line when I input Korean letters at this URL, https://ko.wikipedia.org/w/index.php?title=%EC%82%AC%EC%9A%A9%EC%9E%90%ED%86%A0%EB%A1%A0:Ryuch/%EC%97%B0%EC%8A%B5%EC%9E%A5&action=edit&redlink=1 .
You can see how it works at the video clip on youtube. https://www.youtube.com/watch?v=IOQm7y-IIC0
<del>And another problem for me is that I do not know when it occurs. </del>
When you create a new article with Visual Editor on KOWP, you have the problem.
But I have not experienced it on ENWP.