When hovering is enabled QQuickWindowPrivate::deliverTouchAsMouse sends a QEvent::MouseMove after a Qt::TouchPointReleased. But when no mouse has been used before ( f.e. when no mouse is connected ) QGuiApplicationPrivate::lastCursorPosition is undefined ( inf, inf ) and the event contains totally useless data ( localPos=2.14748e+09,2.14748e+09, screenPos=inf,inf )
Having hovering enabled, when using touch inputs sounds like not making a lot of sense, but applications that are written to run in all kind of environments will have this combination.
A potential fix should be easy: only sending a MouseMove, when QGuiApplicationPrivate::lastCursorPosition is valid.
Guess the issue can be found in many versions not only Qt 5.11