Misc bugs

[C7]

https://www.youtube.com/watch?v=5U6C3W_g-SQ&feature=youtu.be
EDIT:
 Log file https://mega.co.nz/#!EYszVSQB!hZwTEgLdyOBHJLbGE0-Mg8zUaVQZdSCf7ZcekR5pfdA

This is a bug that we've seen before with collisions, where the forces can become NaN, when that happens the NaNs cause the rendering to fail. Thank you for the log file, we're working on getting this one fixed.