w3dut, the dump is not clear about what happens.
You can try to select the whole object and apply Cleanup command (in Body mode) before execute the command - maybe it could be caused for some bad geometry, since the process is pointing the reason as a badarg...
I noticed that you are using the 1.4.1 version and I would suggest you to try wings-1.4.1.137.g5ee2.exe that have lot of bug fixes (even, this problem seems to not be related to any of them).
You can try to select the whole object and apply Cleanup command (in Body mode) before execute the command - maybe it could be caused for some bad geometry, since the process is pointing the reason as a badarg...
I noticed that you are using the 1.4.1 version and I would suggest you to try wings-1.4.1.137.g5ee2.exe that have lot of bug fixes (even, this problem seems to not be related to any of them).