Strange binding behaviour in QtQuick

I encountered a strange binding behaviour in QtQuick, which might well be related to me misunderstanding certain concepts,
although I suspect it to be a bug.

I attached a small QML example below; it contains 2 slider and 2 switch controls, which are mutually bound to each other.
In other words, if you move one slider, the other follows; if you toggle one switch, the other follows and vice versa.
This works as intended for the sliders, but fails for the switches. If you toggle one switch, the other will follow,
but if you then toggle the other switch, the connection is broken. It does not matter, which switch you start with;
the connection is kept until the other switch is touched - then the whole binding between the switches breaks down.
Is this a bug, or am I seriously missing something? A possible culprit could be the fact, that the switch is animated,
while the slider is not.