QMainWindow with many text widgets: background application visible when Split view focus changed between qwerty and alphanum. virtual keyboard

Preconditions:

Application includes QMainWindow with many QWidgets that supports text input. Tested with QLineEdit, QPlainTextEdit,QSpinBox, QDateTimeEdit.
Text widgets are vertically centered on application screen, partially or completely out of split view screen area (=bottom or center of the screen or fullscreen).
Note: this error is not reproduced if text widgets are on top of the screen i.e. they fit into split view screen area.
Application is on portrait mode.

Test steps:
1. Tap the QDateTimeEdit on application screen
--> split view is opened with qwerty keyboard.
2. Change focus to QSpinBox.

Expected result:
Split view is opened with alphanumeric keyboard.

Actual result:
Background application (e.g. application grid) is shortly displayed on virtual keyboard area before the split view is opened with alphanumeric keyboard. Same happens also when the focus is changed from QSpinBox to QPlainTextEdit and virtual keyboard is changed from alphanumeric to qwerty.