bhyve VM causes system crash

[Yuri]

I run VBox without problems. But after I added bhyve VM, I noticed that 
this system becomes likely to crash after some time. It first works, but 
in a few hours system crashes.

So it is either bhyve that is unstable itself, or there is some conflict 
between bhyve and VBox, because they both use hypervisor. (just an idea)

Anybody knows what is the likely reason why bhyve is causing crashes?

Yuri