I'm almost positive that the corner stand is a protective/safe stance for them. Secret was in a round cage for years and it messed with her head.... she actually does loops in her cage when she's flustered now. Rarely, rarely happens now.
Remember the amazon will feed off your emotions. If you are calm, she will feel it. If you are panicky..... well, you'll see. Watch the eyes, watch the tail flares. They're easy to read (except when they are sneaky and there are a few here on the forum that may have developed that).