When I extract the p-values from coint2 with restricted exogenous variables I receive a warning and a column of nans

? coint2 4 endo; d_IAU; IAU --crt --silent
? eval $pvalue
    0,021269          nan 
     0,88179          nan 
     0,68159          nan 

Warning: generated non-finite values

Is this intended? Can I suppress the warning?

Best
Andreas