SteveS, are you confident your Amazon stuff is not related caching of content within your site by AWS Cloud Computing /Route 53?
https://aws.amazon.com/Additional reading at:
https://en.wikipedia.org/wiki/Amazon_Route_53The IP 72.21.217.n has been used as a proxy for a User Agent of MSIE-6, which is in itself highly deprecated. Headers can also be consistent with either a battened-down proxy or a bot.
Additional reading at:
"amazonaws.com plays host to wide variety of bad bots"
https://www.webmasterworld.com/search_engine_spiders/3828718.htm