Impacted versions:
9.0 Community & 9.0 Enterprise

Steps to reproduce:
- Open up a V9 runbot
- Go to projects and click on the issues item, for example for the project 'Research & Development':
  ![image](https://cloud.githubusercontent.com/assets/6352350/13873686/65f2c31c-ecf3-11e5-917a-38df2832bd00.png)
- The project tasks view is opened in place of the project issues. (notice that this only happens every once in a while, about once in five attempts) Example:
  ![image](https://cloud.githubusercontent.com/assets/6352350/13873789/14798b64-ecf4-11e5-9b77-f2ad5d3a8adc.png)

Current behavior:
Every once in a while (about one out of five attempts) after clicking on the issues button it will open up the project tasks, not the issues.

Expected behavior:
When you click on the issues the view with all issues opens, not the view for all tasks.

""" Gives default stage_id """
        if context is None:
            context = {}
        return self.stage_find(cr, uid, [], context.get('default_project_id'), [('fold', '=', False)], context=context)
    def _read_group_stage_ids(self, cr, uid, ids, domain, read_group_order=None, access_rights_uid=None, context=None):
        if context is None:
            context = {}
        access_rights_uid = access_rights_uid or uid
        stage_obj = self.pool.get('project.task.type')
        order = stage_obj._order
        
        if read_group_order == 'stage_id desc':
            order = "%s desc" % order
        
        if 'default_project_id' in context:
            search_domain = ['|', ('project_ids', '=', context['default_project_id']), ('id', 'in', ids)]
        else:
            search_domain = [('id', 'in', ids)]
        
        stage_ids = stage_obj._search(cr, uid, search_domain, order=order, access_rights_uid=access_rights_uid, context=context)
        result = stage_obj.name_get(cr, access_rights_uid, stage_ids, context=context)
        
        result.sort(lambda x, y: cmp(stage_ids.index(x[0]), stage_ids.index(y[0])))
        fold = {}
        for stage in stage_obj.browse(cr, access_rights_uid, stage_ids, context=context):
            fold[stage.id] = stage.fold or False
        return result, fold
    def _compute_day(self, cr, uid, ids, fields, args, context=None):