Symptoms
Activity destination user error
Diagnoses
The problem with obtaining activity destination user in workflow. I need this user history record. To start this Activity a Default Client Event has been used.. After that use a SmartObject Event which takes Activity Destination Instance User's Name and use it in as a history record, You receive the name of account under that runs K2 host server - not the name of destination user
Resolution
I advised the c to change the destination rule to something else such as Plan Per Destination - All at Once.
Please have a look below at all the destination rules.
http://help.k2.com/onlinehelp/k2blackpearl/userguide/4.6.7/webframe.html_destination_rule-destination_rule_options.html
The reason why this happens is because the default method 'Plan just once' will only execute the instance once only, thus only one task item is created and the rights are assigned to the only single task item.