It just occurred to me that some apparent indeterminacy may result from whether I am signed in to my account. I never know whether I'm signed in until I'm asked to enter my password, meaning I'm not, because only some operations require being signed in, and I'm signed out automatically after some time has passed. It's hard to keep track of when I keep an Amazon tab open long term. The system won't do the one click ordering thing unless it's sure I'm me.
Greg (retired in 2010 at age 68, state pension)