What is the test for reversal of a verdict when the jury instruction is factually unsupported?

In summary, in cases where a jury instruction is factually unsupported, "affirmance is the norm." (People v. Guiton, supra, 4 Cal.4th at p. 1129.) "If the inadequacy of proof is purely factual, of a kind the jury is fully equipped to detect, reversal is not required whenever a valid ground for the verdict remains, absent an affirmative indication in the record that the verdict actually did rest on the inadequate ground." (Ibid.) The verdict here was based on valid grounds.