When I copy a drawing to a new frame it turns black

[Mathilde Ellegaard5D58]

Hello. I have a problem, and I'll try to explain it as good as I can. I'm making a video right now, and when I copy some of a drawing and paste it on a new frame, with an already existing drawing, some of it turns black. I hope you can help. 
I'll try and show it with pictures here:

[Mario_CR]

This usually happens when your shapes have too many anchor points. Try optimizing your drawing by going to Modify > Shape > Optimize... or press Ctrl+Alt+Shift+C, and try again.