I did not get any answers and did not solve the problem, but I found a (not so nice) temporary solution: for example, lines like

r:=traperror(NormalForm(g,AA,matermorder)); if r=`polynomials not members of the algebra` or nops(AA)<2 then

I replaced by

try r:=NormalForm(g,AA,matermorder); catch: r:=11;  end try; if r=11 or nops(AA)<2 then

Obviously, if the error is not "polynomials must be members of the algebra" but something different, the exception will be processed incorrectly, but at least I obtained the same output as the author of the software. Still, I am very interested in a correct solution.

Thank you