The QtQuick Controls 2 component "TextField" inherits from QtQuick 2.7 "TextInput". The signal "editingFinished" was added to TextInput in Qt 5.2.
Under certain circumstances, using "onEditingFinished" causes the following runtime error: ".onEditingFinished" is not available due to component versioning.
I've attached 3 files to demonstrate the problem.
1) The code in "main.qml" works as expected.
2) The code in Page1Form.ui.qml and Page1.qml fails with said runtime error.
The bug was reported to affect Qt 5.7.1 by a user on the forum, see: https://forum.qt.io/topic/77642. I reproduced it with 5.8.0.