BEPUphysics

I have tried to convert my xna project to monogame, most of it works fine except for this bug:
https://www.youtube.com/watch?v=TO8NTwPhoIg
Why does this happens? In xna my code worked perfectly.

Sorry, I'm not sure what you mean.

If this is a strictly graphics related problem, my recommendation would be to ask on the monogame discussion boards.