VOLU_ASSEMBLYs are not being added to the geometry. This is demonstrated in examples/extended/persistency/P03 Rename g4geom_assembly.txt to g4geom.txt and then run textGeom The issue appears to have been introduced in version 9.4. It can be resolved by removing the else statement on line 164 in G4tgbVolume.cc in the method G4tgbVolume::ConstructG4Volumes This else statement prevents the Assembly tree from being traversed and the volumes within the assembly being added to the geometry.
I should add that the source file references are from the 9.6 release.