Hi Sebastian - that's not an error message from MoI, it appears to be a message that Alibre is showing is that correct?

You would need to ask them what "Object reference not set to an instance of an object" means exactly but it sounds like some kind of debugging log output.

Do you possibly have any surfaces in your file that are badly structured like with self intersecting areas? Things like that could cause various problems.

You also might try using a different file format for the transfer and see if it goes better, give SAT format a try.

- Michael