Look - TBH I noticed it ages ago (years) and thought nothing of it.
Let me clear cache.
I replicated it 6 times in a row. For a total of about 10 times now.
I recall this from somewhere else. Perhaps there is an odd impact from one of my add ons. Hold up: I had ad block installed, but disabling it did nothing (cleared cache again just in case).
I tried to remove the security certr (made https into http) but that did nothing. I will test on another machine tomorrow.
Let me know if you need me to try anything else.