Not a lawyer, but even if the FBI had "exonerated" Manafort in the past, that is not the same as a trial, so no double jeopardy would apply. If the things they seized from Manafort were authorized by a search warrant, then the judge who issued the warrant must be put on the stand and questioned by the defense, and he would most likely still be upheld.
I too searched for articles on this, but I couldn't find one. This is something I received in an email a while back.
Judge Nap says Manafort’s defense will be that he was EXONERATED 8 years ago…