Some of our customers cannot input Korean or Traditional Chinese

Recently, some of our customers have frequently reported that they are unable to input Chinese in our application, while it works fine in other applications. From the screenshots provided by users, we observed that our application switches to the English input method without the Global icon, only displaying the Emoji icon. However, in other applications, this issue does not occur.

And also we cannot reproduce this issue by our self.

It seems we cannot change keyboard programmatically since iOS 13, does any have any ideas about this?

Some of our customers cannot input Korean or Traditional Chinese
 
 
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