That looks like a weird renpy timing issue (not part of my game code). No idea what could cause it...
In my next game I will definitely have performance in the back of my head when coding.
I usually code on my mac and test the windows version in parallels/virtual machine, so the win code runs in an awfully slow environment. Haven't seen above issue there, though. But some timing issues with screen.rpy have occurred (especially tooltip features)