Coupling error: external structural force

Hello, I'm trying to run the case of a rotor using the Mbdyn - Dust coupling. In the input file for Mbdyn the force is defined with:

force: 1, external structural,
		socket,
		create, yes,
		path, "$MBSOCK",
		no signal,
		coupling, tight, # loose
		sorted, yes,
		orientation, orientation vector,
		accelerations, yes,
		4,
		41, 11, 43, 13 ; 

The output generated is the following one:

Creating scalar solver with Naive linear solver
Reading Structural(1)
Reading Structural(2)
Reading Structural(3)
Reading Structural(4)
Reading Structural(41)
Reading Structural(43)
Reading Structural(11)
Reading Structural(13)
Reading Joint(1)
Reading Body(2)
Reading Body(3)
Reading Beam(123)
Reading Joint(2)
Reading Joint(11)
Reading Joint(21)
Reading Body(11)
Reading Joint(12)
Reading Joint(22)
Reading Joint(13)
Reading Joint(23)
Reading Body(13)
Reading Joint(14)
Reading Joint(24)
Reading Force(9)
 self.socket.nnodes:  4
LOCAL connection to path="/tmp/.mbdyn_0_f3doy8/mbdyn.sock"
Initial assembly iterations reached maximum number 0; aborting...
An error occurred during the execution of MBDyn; aborting...
recv(cmd=7) failed, rc: -1, sizeof(mbc->cmd): 1, errno: 104, err msg:
mbc_py_nodal_negotiate: error
Traceback (most recent call last):
  File "/home/anlattan/work/dust/examples/caradonna_coupled/main.py", line 44, in <module>
    run_precice(path, dt, path2mbdyn)
  File "/home/anlattan/work/dust/utils/adapter/run_precice.py", line 68, in run_precice
    mbd.initialize( path=path, verbose=1, nnodes=nnodes, accels=1, \
  File "/home/anlattan/work/dust/utils/adapter/mbdynInterface.py", line 80, in initialize
    self.nodal.negotiate()
  File "/usr/local/mbdyn/libexec/mbpy/mbc_py_interface.py", line 52, in negotiate
    raise Exception;
    ^^^^^^^^^^^^^^^
Exception

Does somebody know how can I fix that? Thanks in advance.