is tax basis for inherited stocks & bonds the death date of the decedent or the date the brokerage firm unfreezes his account?

I inherited stocks and bonds from a relative.Normally the cost basis is the date of the decedent's death.The brokerage firm locked the accounts until they received letters of testamentary from the probate court. There were delays by the court and the stocks and bonds decreased in value. Does this change the basis date to when the funds were available?