We are investigating this issue now. Updates will be posted here as we learn more.
UPDATE 13:50 GMT
We are now moving on to repairing the data. The aim is to restore the teams who were removed from leagues and any designs or money they lost in the process. Thank you for your patience as we do this.
As a side note: In the process of investigating this I have found a noteworthy gain in efficiency on the related code. Once things are back online, they should run even better than before... the only piece of good news to come out of this situation.
UPDATE 13:11 GMT
We have identified and patched the underlying cause of this. We will now be working on repairing any affected data and seeing how we can best restore affected teams to their leagues and restore their designs etc.
We believe 2000 teams were affected by this in total, and it was a glitch whereby dates in the system were interpreted incorrectly. Thereby, managers were detected as inactive when they were actually active.