What is the test for "processing errors" in the context of a motion?

… The phrase “processing errors” is borrowed from Keljanovic Estate v. Sanseverino, supra, at 489-90 where O’Connor J.A., for the majority, said: The second kind of error that may warrant appellate interference is what might be called a “processing error”, that is an error in processing the evidence that leads to a finding of fact. This type of error arises when a trial judge fails to appreciate the evidence relevant to a factual issue, either by disregarding or misapprehending that evidence. When the appellate court finds such an error it must first determine the effect of that error on the trial judge’s reasoning. It may interfere with the trial judge’s finding if it concludes that the part of the trial judge’s reasoning process that was tainted by the error was essential to the challenged finding of fact. …