Portfolio 7 Multiple boards / Sprints showing up in Velocity Charts

[E]

We are running JIRA 7.1.7 with Portfolio 2.0.3

When i load up a teams board and then go to reports and select Velocity chart i see sprints which are not associated with the teams board or filter query. 

Any ideas what could be going on?

[Jakub Pierzchała]

Perhaps multiple teams are working on the same JIRA project? As far as I know, Sprints are linked to projects, not teams.

[E]

Yes all teams are using the same project with different backlogs etc. This is a feature which was a LABS feature of JIRA 6.x but became a full feature in JIRA 7.

Multiple consecutive sprints i believe is what it's called.

We typically see this behaviour when team data gets "Shared" or tickets get assigned to more than one team but i cannot find an instance of that.