afraid you will also need to add to the main script (for now, while we fix this correctly)

#where variables are added

model_part.AddNodalSolutionStepVariable(ROTATION)

model_part.AddNodalSolutionStepVariable(MOMENTUM)

and

for node in model_part.Nodes:

node.AddDof(ROTATION_X, MOMENTUM_X); #ATTENTION: added by Riccardo

node.AddDof(ROTATION_Y, MOMENTUM_Y); #ATTENTION: added by Riccardo

node.AddDof(ROTATION_Z, MOMENTUM_Z); #ATTENTION: added by Riccardo

where dofs is added

this problem rises since JM removed such variables from the "mechanical solver" thus breaking the solver itself for

applications that do require this variables.

We'll work on fixing this asap.