Play Preview Problem - Player rescales once you start the preview, making the prototype unresponsive

Hello there!
As you can see in the video and pictures (see attached video & pics), once i start the preview (crtl+enter / click on the play button) the player opens and it starts with a wider size than my artboard, then quickly rescales it's witdth to the correct size (or at least this is what i make of it).

While the rescaling (or whatever it's doing) happens, the prototype is unresponsive, i can't click anything. 

I've been having this issue for a couple of weeks now (around the 1st of July) and i would appreciate it if someone can take a look. 

Thanks a bunch.