[translated comment from licensee]
This issue can be found in a IOS project using the Integrated Keyboard.
it occurs when using a Japanese keyboard on EditableTextBox.
There is no problem with English and Korean keyboards.
It seems that there is no problem with the touch input itself, as I can find log Got a keyboard call, line ###.
When the keyboard is activated, the popup UIView does not disappear completely after being called from FIOS PlatformTextField::ShowVirtualKeyboard(), so the keyboard is processing the input of a certain area at the top of the screen.
When I printed value of the CGRect.size.height in UIKeyboardFrame in Korean and English keyboard View. it is different from the value of the Japanese keyboard. the height value was 209.0 for Korean/English and 203.0 for Japanese keyboard.
As a result of this difference, when the keyboard is hidden, the keyboard view does not move enough.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-148109 in the post.