Error: "non-conformable arguments"

Hello everyone!
I am trying to fit a latent (linear) growth model (with genetic and environmental influences, ACE) using ordinal twin data (MZ and same-sex + opposite-sex DZ; 6 groups), which includes 3 variables, 7 categories in each of them. The definition of the thresholds (invariant thresholds) seems to be difficult and the execution of the script returns:

"Error: The algebra 'ACE.ThInc' in model 'lgcOrdACE' generated the error message: non-conformable arguments"

Any help to interpret this error message would be very much appreciated. Is there any possibility to solve it? I have attached the script with the model to help with the issue, in case somebody want to have a look.

Thanks a lot beforehand!
Regards,
Alfredo