Check if the input line (swype) is working in Gboard (I'm working on russian layout). Or install SwipeKey.
It's enough to quickly-click on TextEdit, and the text starts to randomly change
Bug is more pronounced with selectByMouse: true

with inputMethodHints:  Qt.ImhSensitiveData /  Qt.ImhNoPredictiveText all ok,but the ability to use keyboard words is lost

(predictive input = when a line appears under text, and swype works)

For SwiftKey: just install SwiftKey with default settings

Next, choose any editable Qt-text (for example, TextField).
For SwiftKey (easy to reproduce): move cursor several times from beginning to end and back
For gboard (more difficult): need to click on random places in the text field until the text changes (personally I have two languages at gboard. In english layout, swype does not work on the keyboard, and there are no problems. In russian works and the problem is)

Actual result: text loss, text symbols are mixed
Expected result: stable work with text