Copy extended types gives access violation

Hi

I get an access violation when I try to copy one extended structure to another:

"forrtl: severe (157): Program Exception - access violation"

If I use ordinary "types", then this works fine.

Am I not allowed to copy one extended type to another? Is there are workaround?

I am using the Intel Visual Fortran Compiler v. 16.0.

    program Console1

    implicit none

    ! Variables
    integer, parameter :: DP=8
    integer, parameter :: MAXNAMELENGTH=10

!-- BASIC TYPE
    type :: T_BASIC(n)
      integer, len                    :: n=MAXNAMELENGTH  !length of nam (defaults to MAXNAMELENGTH)
      character(len=n)                :: nam    !name
      integer                         :: iPoi   !internal pointer
    end type T_BASIC

   
!-- beam appurtenance properties
    type, extends(T_BASIC) :: T_prtapp    !<- **** this will lead to trouble ****
!    type :: T_prtapp                     !<- **** this will work            ****
      integer                                         :: Tp
    end type T_prtapp
   
!-- beam appurtenances (actual appurtenances as used)
    type :: T_bapp
      type (T_prtapp)                                 :: prt     !appurtenance properties for this beam appurtenance
     
    end type T_bapp
   
!-- Global data
    type :: T_G
      type(T_prtapp), dimension(:), allocatable         :: prtapp  !appurtenance properties
      integer                                           :: nprtapp !number of appurtenance properties
     
      type(T_bapp), dimension(:), allocatable           :: Bapp     !beam appurtenances
      integer                                           :: nBApp    !number of beam appurtenances
     
    end type T_G
    type(T_G) :: G
    integer   :: iret
   
   
    ! Body of Console1
    G%nprtapp = 5
    allocate(G%prtapp(G%nprtapp))
   
    G%nBapp = 3
    allocate(G%Bapp(G%nBapp))
   
    G%Bapp(1)%prt = G%prtapp(1)   !<- this throws the error

    iret = 1
   
   
    end program Console1

Best regards

Lars