Unable to update the project team

Hi, I'm having a problem with translation projects. Only the admin user can see them.

When I try do add a team member I get:

Caused by: com.adobe.cq.projects.impl.team.TeamException: The team does not contain an owner at com.adobe.cq.projects.impl.team.TeamManagerImpl.createTeamMemberList(TeamManagerImpl.java:146) at com.adobe.cq.projects.impl.team.TeamManagerImpl.createTeamMemberList(TeamManagerImpl.java:94) at com.adobe.cq.projects.impl.team.TeamManagerImpl.updateRoleGroups(TeamManagerImpl.java:569) at com.adobe.cq.projects.impl.ProjectImpl.updateMembers(ProjectImpl.java:115) ... 133 common frames omitted

But, when I try to add an owner I get:

30.09.2016 06:57:26.097 *ERROR* [127.0.0.1 [1475218646094] POST /content/projects/20160720/englishtogermantranslation HTTP/1.1] com.adobe.cq.projects.impl.servlet.ProjectServlet Unable to update the project team java.lang.NullPointerException: null at com.adobe.cq.projects.impl.team.TeamManagerImpl.adjustGroupMembers(TeamManagerImpl.java:650) at com.adobe.cq.projects.impl.team.TeamManagerImpl.adjustMasterProjectGroup(TeamManagerImpl.java:631) at com.adobe.cq.projects.impl.team.TeamManagerImpl.updateRoleGroups(TeamManagerImpl.java:575) at com.adobe.cq.projects.impl.ProjectImpl.updateMembers(ProjectImpl.java:115) at com.adobe.cq.projects.impl.servlet.ProjectServletUtil.updateProjectTeam(ProjectServletUtil.java:238) at com.adobe.cq.projects.impl.servlet.ProjectServletUtil.updateProjectTeam(ProjectServletUtil.java:232) at com.adobe.cq.projects.impl.servlet.ProjectUpdateServlet.doOperationUpdateTeam(ProjectUpdateServlet.java:825) at com.adobe.cq.projects.impl.servlet.ProjectUpdateServlet.doPost(ProjectUpdateServlet.java:158) at org.apache.sling.api.servlets.SlingAllMethodsServlet.mayService(SlingAllMethodsServlet.java:149) ...

Any suggestion on what can be wrong / what to try?

Thx,

Federico