Not sure if this qualifies as a bug, but printing an envelope with a width of less than 8.38" (i.e., 8 3/8") causes the printed address to be rotated 90 degrees. It turns out that this isn’t really a problem. You can just use a width longer than 8.38" making sure the address field stays within the actual width of the envelope.
Please remove this “question”, and instead post this as an answer to your older question. So instead of two unanswered and unrelated questions, we have one with an answer/explanation. Thanks!