Procedure to get Title Clear Certificate

Mr A purchased a flat registered deed from builder on18/06/2004 obtained home loan from nationalized bank,in july 2004. Mr A was failed to repay home loan, bank took possession of flat & auctioned it under SERFASEI act 2002,Mr B purchased flat from bank on 20/02/2007, later on sold it to Mr C. on 16/10/2012 after few years Mr C decide to sell then the purchaser got search report , which shows two more registered transactions of same flat, 1.builder sell agreement with Mr A (same flat ) after bank loan( i think bank unknown of both development) on 10/11/2004 the builder executed two sale deeds for the same flat and registered both of them in favour of A on two different dates? (One on 18/06/2004 and another on 10/11/2005). 2.Mr A sold same flat to Mr D on 14/07/2005 ( after this bank possession and Auction done as bank rule ) i would like to know who is actual owner of flat, & from whom to approach to get clear title of flat what legal step can be taken .