Question: Different order of terms each time I clicked !!!

Hello people in mapleprimes,
I have a question.
I appended two pictures where from the same code, two different orders of
expression appear.
How can I do for this so as not to get error messages?
The cause of this is simplify(%,symbolic) brings different order of term a__0^(-k)*F__D ahead of a parenthesis in a jpg.file and F__D*a__0^(-k) after
that parenthesis in another jpg.fine both in the line above that of  "dairihensu1."

In this case, What I can do?
Please help me.
Best wishes.

taro

my_code.mw

Original code is

e7_4:=F__D*(Omega+1)*beta/(beta-1) = F__I*a__D^(-k)*a__0^k+T^((sigma-k-1)/(-1+sigma))*F__D*phi^(k/(-1+sigma))+F__D;

a1:=beta=k/(sigma-1);
subs_free:=
  proc(a,b,c)
    local b1;
    b1:=isolate(b,c);
    subs(b1,a);
  end proc;
isolate(e7_4,a__D^(-k));simplify(%,symbolic);dairihensu1:=subs_free(%,a1,sigma);e7_5:=applyop(simplify,[2,4,1,3,2],dairihensu1);

A case without error.

A case with a error.