Hello and thank you for making Prism I just bought it. I hope this bug report helps.
v 0.1.0.2944 on OSX
The whole window shows a repeated copy of the screen complete with mouse pointer, shifted off to the side on a dark grey background. It's very distracting and looks quite yucky but it seems to just be a visual glitch. The mouse pointer(s) correctly click the on-screen button(s). Plural because there are duplicates on the screen.