I'm trying to do some exercise here. Just created a 'Basic Mashup' from Qlik Sense's default mashup templates. I put 4 graphics, each one from a different QVF.
Realized that sometimes it doesn't load correctly the objects. I'd say that, while refreshing 10x the mashup page, 2x the problem occurs.
From my point of view, this could be a bug on the Qlik Engine, since I used the default Qlik template...
Here is an image to ilustrate: