One addition, just a hunch that it might be related:
With the Migration to Generate Press, I included the Link “http://www.myblog.xx/wp-login.php/” to the Main Navigation, that is now shown above the header logo.
So from a rendering viewpoint, “http://www.myblog.xx/wp-login.php/” is now part of every page.
I have a hunch, that this fact might be the Connection to what is going on in the crawler.
What I dont understand and what must be related to Generate Press is, why Googles Crawler creates such a funny link in the following form from it:
“http://www.myblog.xx/wp-login.php?redirect_to=http%3A%2F%2Fwww.myblog.xx%2something%2F”
This Link cant work and must run in a 503. And so it does and creates the crawler errors.
But the Login page itself is fine and fully accessible. Just not the funny link, Google creates somehow. But how? And how is this related to the theme??
Just an additional Information to nail down the cause ….