I have no idea. Maybe the description isn’t stored in the post description field, maybe in a meta? I have a copy of visual composer myself for testing puproses, but it works 🙁
I can’t really provide or promise 3rd party plugin compatibility, but usually visual composer is an exception due to it’s wide user base – and it’s very well written plugin, I must say.
In your case all I can do is manually debug and check for possible errors and such. To do this however I need temporary ftp and admin access. If you can provide that, I will probably be able to tell what’s the problem there. You can do that by editing your first post in this thread, or uploading a txt file with details. Both way is secure, not visible to anyone else.