Hi,
We discussed this case directly via support emails.
In the report, the Assignee dimension was used to retrieve balance by teams. Sprint measures are based on issue change history, therefore, the assignee during each activity (committed, added, removed, at closing) is taken into account independently. Thus, if the user (team) was changed during the sprint, the balance can be changed.
The suggested solution was to create a new JavaScript custom field dimension “Current Assignee” that does not have historical user changes and then filter the balance report by the issue current assignee instead. Here is described how to do that: Pull Transitions by Current Assignee, not Assignee at Time of Transition
How assignee selection impacts sprint scope measures you may watch in the recording of the recent sprint webinar (starting from around 27:00): Sprint Reports with eazyBI - eazyBI
Best,
Ilze, support@eazybi.com