Triangle culling glitch

Hey what's up everyone? There's a really strange thing happening: some triangles are getting culled in our game. You can see it here in bottom left corner: https://youtu.be/I3WK5EvVMw8 We don't use occlusion culling, so I blame it for frustum culling for camera. But after reading the documentation it's apparent that frustum culling cuts the whole object, not a single triangle. So, any ideas what the problem would be? Cheers, Vlad