I have to report a bug in version 3.4.3 of GAP.
It does not cause wrong results.
But it may happen that GAP signals an error when computing
the intersection of two AG groups.
This bug can be fixed by replacing the assignment
B := Base( V );
in the definition of 'AgGroupOps.AffineOperation' in file 'agsubgrp.g'
if IsRec( V ) then B := BasisVectors( Basis( V ) ); else B := V; fi;
Sorry for the inconveniences