Model behaves abnormally when scaled (not always), video.

[XMight]

Hello,
I have a problem. I import a model in my app, and I create a soft body from it (btSoftBody). I scale it by the factor 2.0 and it runs OK. But I need to scale the model by 4.0. If I do so, the model lasts 1-2 seconds, then explodes/disappears in some cases. In the case of the video presented below, it behaves abnormally. (my simulation is turned off, and I turn it on manually, so I see initially the correct model).

Why is that, any suggestions?


P.S. The model is loaded inside a box world, with the size 80.0, 80.0, 80.0. The model has the size: outer 0.6 diameter, 4 height, 80 vertices, triangulated, so if I scale it 4 times or even more, it must fit in the box. (a tube is my model)

The video that demonstrates the behavior:
http://www.youtube.com/watch?v=xUDp0KwGQoI