It's happening to me for a long period of time. Happened on more than one computer.
I am not kept logged in even if I click "Keep me logged in" at the login screen.
There's a 'timeout' that sends users to Career centre if OSM tab is inactive for more than 10 minutes. This was necessary because a lot of info changes on OSM (player prices, league vacancies, etc, etc....).
By not forcing this 'refresh' o flocal info we were getting a lot of reports of errors that weren't nothing more than attempt to do something that was no longer valid, so we implemented this system to force the refresh and reduce these reports and also some real errors caused by this!
What you need to do is just stay active on OSM to avoid this!