Window Hipchat client have a problem with input multi-byte characters.

Hi, I'm using HipChat window client in Windows7.
When I tried to input a single-byte word after the end of multi-byte word,
the HipChat client make a copy the last multi-byte character.

I expected: '안녕? 이것은 예시 입력. '
The result: '안녕녕? 이것은은 예시시 입력력. '

I updated HipChat client two days ago (2015-12-02),
All of my co-workers encounter same bugs with window standalone client,
But this bug is not reproduce in web-client.

And today I update lastest version (4.0.1610),
But the bug is not-disappeared.