Appellate arguments that are not waived by the appeal waiver in a plea agreement

In U.S. v. Romero, the Fourth Circuit in a per curiam opinion for the panel of Judges Niemeyer, Agee, and Diaz ruled that the appellant's three arguments raised on appeal were each of them within exceptions to the general rule that appeal waivers are enforceable, but the arguments were not established by the record or premature.