They had 4 rounds of java interview process. Twice they have asked for documents to process the offer letter but later denied saying that you don't have stability that too after completing all the interview round.
They have poor negotiations on salary part too, first they will quote X amount and then by themselves will say the X amount is too high.
I would suggest that before giving the interview kindly confirm with HR if they are serious in considering the candidate. Also, never believe the salary compensation they offer you, as same thing have happen with me post explaining me the break up structure they have denied the offer letter.