I found a way to the login page.
Go via the register page and submit the button without filling in any info takes me to the login page.
about 3 nights ago, using chrome on the desktop, i came across your exact same issue of not being able to access the login page at all.
i was successfully able to do it on ie11, edge, firefox, firefox mobile, and chrome mobile. but not desktop chrome.
ill see if i can reproduce the issue again tonight, and then use your procedure to bypass the bug with that. i can then attempt to track down things a bit further.
this is a bug. it should not be happening. it never presented itself during the 8 months of testing the new(ish) login script lines.
this is a bug, i too have seen with my own eyes.
thanks morgan, for this tip!