I have the same issue. It happens every 30 Minutes or so, then after 5-15 Minutes I can access the wp-admin panel again. On the regular domain that I linked to the Main Page of my site the user is asked to install wordpress, and I am asked to install it. When I do a long error log appears, and then after some time i get the message that Wordpress appears to be already installed, then I can login and access everything again.
Help please.
Right now (we are 10 hours later compared to your message), it is still the same 