Many people think that it HO allotment who is responsible for Degrading a WL/CNF ticket in to WL/WL status.
This is not correct.
The common reason for such down grading (and it happens with AC class mostly) is:
Last minute removal of Coach at "washing pit" called 'coach certified as Damaged' in Rail lingo. and unavailability of spare coach (specially AC coach.
This...
more... results reCharting (some time) or Charting minus damaged coach.