Without my having made any changes the Amazon Captcha problem ended about 8/5. It was happening more frequently than the sync interval and hasn't happened at all in the last 2 days. But at that same time I had the ebay problem which after deleting and re-entering the ebay account that now works properly too.
Since the last app update was June 10 I assumed something was fixed in the support services somewhere.
Running app on a Motorola Moto G XT1032 running Android 5.1.