I'm sorry that I don't have an answer for you, however, I completely empathise with your problem. I too have been going around in circles for days and am at the point of considering rolling back to, what I consider, a more stable version of Moodle.
My current problem is that I'm the only admin, I can access the admin part of the website, make any changes I feel like making, but as soon as I enter the learning part of the site, I'm treated like a guest and can pretty well do nothing. I'm feeling very sad about this