Wrong size for finite deleted permutation module

[ssiccha]

The following loop quite quickly leads to an incorrect size:

gap> testFDPM := function(deg, field, alternating)
> local g, gens, mgens, m, cf, dims, max, pos, x, h, result;
> if alternating then
>   g := AlternatingGroup(deg);
> else
>   g := SymmetricGroup(deg);
> fi;
> gens := List([1..5],x->PseudoRandom(g));
> mgens := List(gens,x->PermutationMat(x,deg,field));
> m := GModuleByMats(mgens,field);
> cf := MTX.CompositionFactors(m);
> dims := List(cf,x->x.dimension);
> max := Maximum(dims);
> pos := Position(dims,max);
> x := PseudoRandom(GL(max,field));
> mgens := List(cf[pos].generators,y->y^x);
> h := Group(mgens);
> return Size(RecogniseGroup(h)) = Size(g);
> #return RECOG.TestGroup(h,false,Size(g));
> end;;

gap> bool := false;
gap> while testFDPM(10, GF(7), bool) do
> bool := not bool;
> od;

This probably will be solved once #265 is merged in. But, that would only hide the error underlying this issue. Somewhere either the immediate verification is not strong enough or there is a bug.