Investigating Prius engine knock poll

We're trying to characterize what it takes to reproduce the 1.8L Prius, cold-start, engine knock. It is intermittent and rare but if we can come up with a protocol that reliably reproduces it, we have a chance of getting effective, corrective action. If you've had the knock, recently, please take the poll and add any additional details that might lead to reproducing this problem at will:

Reproducable knock? | PriusChat

Thanks,
Bob Wilson