It reminds me of an animation job I was working on in Infini-D
Wow, that brings back memories. I used Infini-D back in the day. It didn't even have bones. Any mesh deformation had to be done on the vertex level.
About the black pixels, I've seen that in v14-v15. Most times, if you just rerender those specific frames, the dots will disappear. Sometimes, un-checking Multipass > Soften will get rid of the black pixels. Sometimes I would just have to paint them out. Painting frames is a hassle when rendering an animation, but it's doable. If you render foreground, middle, background in separate passes it seems to help. Also, it cuts down or re-render times too, since usually a problem only occurs on one of the render layers, and each pass takes a lot less time to render than if you render everything in one pass.