Upgrade to 4.50.4 and now get logon error.

After upgrading to 4.50.4 from 4.40.4 I get an error logging on. I cleared the nopcommerce cache, tried running in private mode, cleared browser cache, etc and nothing helped.
The logon actually did work, I just get redirected to an error page instead of the site homepage.

I would appreciate if anyone has a fix for this! Thanks! :)

Here is the sequence of events with the server address redacted:

logon page: 200 OK (get): This is where I enter my credentials.
https://mysite.net/nc_beta/login?returnUrl=%2Fnc_beta

logon page: 302 FOUND, REDIRECT (post): This is what loads after I click the log in button.
https://mysite.net/nc_beta/login?returnurl=%2Fnc_beta

302 FOUND, REDIRECT (get) **** problem step? nc_beta is duplicate!
https://mysite.net/nc_beta/nc_beta

404 (get)
https://mysite.net/nc_beta/page-not-found

302 Found redirect status response code indicates that the resource requested has been temporarily moved.  Do you have any redirection in web.config, redirect plugin, custom code?

Thanks for the reply.
The web.config is stock and contains no redirects.
There is no custom code or modules.

Check the nopCommerce System Log for any errors.