What are the consequences of a federal district court's failure to make findings as to all disputed matters?

Federal Rule of Criminal Procedure 32(c)(1) requires a district court to make findings as to all disputed matters or "a determination that no such finding is necessary because the matter controverted will not be taken in account, or will not affect, sentencing." See also United States v. Fernandez-Angulo, 897 F.2d 1514, 1516 (9th Cir.1990) (en banc). If the district court fails to make the required findings or determinations, the sentence must be vacated and the defendant resentenced. Id.