1993398 - "Adjustments to be made in SPDD transaction" error in ACT_UPG phase during upgrade

• During an upgrade using Software Update Manager (SUM), the phase ACT_UPG is stuck with following similar message:
  
  SUM GUI Screenshot:

Upgrade logs shows:

Directory:    <DIR_PUT>/SUM/abap/log
Name:         SAPupConsole.log:
====================================
>> START OF PHASE MAIN_SHDRUN/ACT_UPG
INFO: shadow instance unlocked.
Synchronizing buffers via 'UPG_BUFFER_SYNC'...
=========== Repository Modifications ===========
You must now include your repository modifications in the new SAP import.
The program has found 13 modified objects that you need to adjust and 0
objects are automatically maintained by import of an adjustment transport that
you have included into this procedure.
To adjust your repository, proceed as follows:
  1.  Logon to the shadow instance as user DDIC in client 000 on server
    <Server Name>.
  2.  Set the 'System Change' option with transaction SE06.
  3.  Create users for modification adjustment by copying user DDIC with
    transaction SU01.
  4.  Logon to the shadow instance as ordinary user and make adjustments with
    transaction SPDD. For more information, see the upgrade guide.

*CAUTION:* If you do not make adjustments now in transaction SPDD, your
modifications will be lost. Even if you do not want to keep your
modifications, use transaction SPDD to reset these objects to the original
version.
01)  -  Adjustments made, continue with procedure
02)  *  Exit program
: Exit program
-- Finished execution of 65/178 phases

• But SPDD shows no objects to adjust(the list is empty):

SAP Netweaver system, Enhancement Package Installation, Release upgrade.

ACT_UPG, SPAU, Adjustments, SPDD, SUM, empty SPDD , KBA , BC-UPG-TLS-TLA , Upgrade tools for ABAP , BC-UPG-ADDON , Upgrade Add-On Components , BC-DWB-DIC-AC , ABAP Dictionary Activation and Conversion , Problem