Hi! this happen on all scene, if I create a cube and I turn on Corona Renderer, if I select "render region" for rendering a little portion of the viewport, the first time all si fine, the second time all si fine, the third time usually I got the spinning ball and all goes to freeze..
If you need I can make a video capture of the situation...
This issue is started with Corona 5...I use Corona 10 hours each day for my job here, and the Corona 4 doesn't had this issue :-/