In my case, the assignments ( or random other data updates ) never happened. In our case, it was SQL related. The DB was overloaded and after records started locking it would cascade into a total meltdown. Even after a restart or letting it sit over night the tickets never got updated and the changes were lost ( which is a bad thing..a REAL bad thing. Its not fun to explain to management or customers why their updates are gone and no way to know what they were )
During the day one sure sign for the users of impending doom was when tickets wouldn't reassign, or lose their assignment totally ( i guess WF would clear current, then add new, and it often would get timeouts on the subsequent 'add' ).
For me, it was when ticket exceptions started piling up due to timeouts in various parts of the flow. Most often they could not be returned until after the server was restarted. I would get perhaps a hundred before the system became unusable and had to be rebooted.