When using Software Renderer (QT_QUICK_BACKEND=software), QML clipping is broken in some cases.
Basically, clipping doesn't work anymore when it is enabled on flickable parent and child items. It also fails when you move an item thanks to a timer.
I attached a QtCreator Project with a single QML file which show 3 cases where clipping fails with Software Renderer although it's okay with ANGLE/OpenGL.
QTBUG-61157 is one of the effects of this bug.
It should be a top priority.