[GAP Forum] bug in StructureDescription?

[Benjamin Sambale]

Hi,

I use GAP 4.5.6 on arch linux 64 bit and just came across the following 
strange behavior:

Define a certain group of order 7^6 by

p:=7;
F:=FreeGroup("a","b","c","d","e","f");
AssignGeneratorVariables(F);
G:=F/[a^p,b^p,c^p,d^p,e^p,f^p,Comm(b,a)*c^-1,Comm(c,a)*d^-1,Comm(d,a)*e^-1,Comm(d,b)*f^-1,Comm(e,b)*f^-1, 
Comm(d,c)*f,Comm(a,e),Comm(a,f),Comm(b,c),Comm(b,f),Comm(c,e),Comm(c,f),Comm(d,e),Comm(d,f),Comm(e,f)];
G:=Image(IsomorphismPermGroup(G));

(sorry for lack of minimality)

Then one can check that:
gap> DerivedSubgroup(G)=FrattiniSubgroup(G);
true

Moreover:
gap> StructureDescription(DerivedSubgroup(G));
"C7 x ((C7 x C7) : C7)"

However:
gap> StructureDescription(FrattiniSubgroup(G));
Error, Record: '<rec>.permpcgsNormalSteps' must have an assigned value

Even more interesting, if I apply the same command again, I get:
gap> StructureDescription(FrattiniSubgroup(G));
Error, illegal access to record component `Unbind(obj.relativeOrders)'
of the object <obj>. (Objects by default do not have record components.
The error might be a relic from translated GAP3 code.)

What is wrong here? (I know that StructureDescription is of little use 
here anyway.)

Benjamin