After using the Groebner and PolynomialIdeals packages, Maple goes into a long calculation when I make an entry of the form

name:=polynomial expression. This can take 10's of minutes for an expression of two lines. The only solution I have found is to save the sheet and restart it and enter the line name:= etc. before loading Groebner and PolynomialIdeals. This is most inconvenient. Is there a better workaround?

I have two polynomials f(x,y,z) and g(x,y,z) and ask MAPLE to find conditions on the coefficients of f and g such that the Jacobian determinant in x and y is purely a polynomial in z. MAPLE finds 4 solutions, one of which is g=0, but does not find the solution f=0. I attach the relevant MAPLE worksheet.