When trying to input with an IME into a text field inside a menu then it will end up putting the text into a different text field. Even though the focus is on the text field inside the menu, it will put the text in the focused widget instead.

In the example attached, switch to an IME (such as Chinese, Japanese or similar), click on the button in the toolbar and then type inside the lineedit. Note it is going to the lineedit underneath instead.